A systematic review of research into executive headship, 2001–2021

While extensive understanding of headship has emerged over the last half-century, the notion of executive headship remains under-explored. This article summarizes a systematic review of evidence relating to executive headship published since 2001. This review found the overwhelming majority of peer-reviewed articles into executive headship are small-scale or largely theoretical in nature. Meanwhile, the few larger-scale studies completed have generally been published directly by their commissioning body. Consequently, much is known about the policy and philosophical drivers behind the emergence of this role in English schools, but markedly less on its operationalization in practice. Furthermore, while few attempts have been made to assess the prevalence of this role, there is nevertheless some evidence (albeit limited) that executive headship can positively impact on organizational effectiveness and pupil outcomes. This article recommends that further research be undertaken into understanding how the role is performed in practice, its strengths and limitations, implications for governance, the characteristics it demands of leaders in practice and the support they require. Furthermore, parallels between this and similar roles in other countries (such as superintendents in the US) should also be examined to identify further lessons on how executive headship can best be utilized both strategically and operationally.


Background
During the last 50 years, school leadership has become one of the foremost areas of interest in educational research.The establishment of the British Educational Leadership, Management and Administration Society (BELMAS) in 1971, and the launch of its journal, Educational Management, Administration and Leadership (EMAL) a year later (followed by a number of other relevant journals), means that much is known about headship, its practice in England and how the role impacts on school effectiveness.
However, the last 20 years has seen an increased divergence in the organization, governance and running of schools which in turn has impacted significantly on the headteacher's role (e.g.Chapman, 2013;Greany, 2015;Tseng, 2015).One example is of this is the emergence in England, of Executive Headship (EH), the origins of which are rooted in the concept of the 'superhead' which itself emerged at the start of this century, and involved 'a trouble-shooter' being 'sent in to sort out' a struggling school (Crawford, 2002).The EH role also gained early momentum from the government's sponsored academies programme, which saw struggling schools removed from local control and instead overseen by sponsor schools or organizations, intent on securing rapid improvements in their performance (Gibson, 2015).
The potential for the EH role was further enhanced by the 2002 Education Act which for the first time, provided a framework for up to five schools to 'federate' and operate under one governing body (Chapman, 2015, Kulz, 2017).The years since have seen growth in such federations but also, more significantly, the rise of multi-academy trusts (MAT), formally constituted partnerships of quasi-independent state schools which receive funding directly from government and potentially provide even greater opportunities for EHs to operate.Indeed there are strong practical and philosophical parallels between EH and the multi-academy trust chief executive officer (MAT CEO) role (e.g.concerning entrepreneurship, networking and civil relationships (Hughes, 2020)), which also extend to comparable roles in other countries (e.g.Superintendents in the US).
However, despite the significance of these trends, relatively little research has been undertaken into EH.This article therefore contributes to both the understanding and development of this and similar roles in other jurisdictions, by summarizing findings from a systematic review of evidence published since 2001.

Aims and approach
The aim of this study was to identify, review and synthesize research completed into EH, thereby bringing cohesion to its research base (Hallinger, 2012).To do so, it utilized Arksey and O'Malley's (2005) scoping study strategy, which Mays et al. (2005) identify as particularly suitable for examining complex or underexplored areas, such as this.Arskey and O'Malley's approach suggests five specific stages.The first identifies the research objectives, which are: RO1: What are the principal foci for studying EH? RO2: What are the main findings from research completed into this area?RO3: What are the implications of this evidence, for practice, policy and future research?
The second stage identified relevant studies, using consistent search parameters to identify items of interest from relevant databases.These parameters combined 'executive head * ' with a variety of other search terms, most notably, 'England' 'English' and 'schools'.Further searches were completed using 'system leaders' and 'system leadership' in place of EH.All searches were completed during February 2021.The EBSCO, Eric and Locate databases were also reviewed using these terms.In total 219 peer-reviewed articles of potential interest were identified.Further exploration of other non-academic databases followed.These searches identified a further seven reports of potential interest.All articles were classified by year, source and the type of evidence provided (e.g.empirical, literature review, theoretical, guidance).
The next stage involved study selection, and saw the abstract and/or executive summary of each article reviewed for relevance.Consequently, 76 articles were shortlisted for a full review.Each document was then reviewed and its key findings summarized in an excel database.This included details of its year of publication, author, source, its evidence base, identified limitations and its main findings.Finally, findings from these materials were identified, organized and summarized under the most significant themes which emerged.

Findings
RO1: What are the principal foci for studying Executive Headship?
Overview of the evidence base on EH Peer-reviewed material.While the earliest study into EH dates back to Barnes (2006), there is remarkably little published, peer-reviewed, empirical research into this subject.There are several reasons for this.Howarth (2015) and Howland (2015) note that in the intervening period the focus for research shifted from EH to structural reform and the growth in MATs, while Boylan (2016) identifies a more general preoccupation with system leadership as a whole rather than EH specifically.
Where research into EH has featured in peer-reviewed publications it has generally summarized small scale, qualitative studies.For instance, Harris et al. (2006), Hatcher (2014), Howland (2015) and Baxter and Wise (2013) all explore EH through single school case studies.
Work by Chapman et al. (e.g. Chapman, 2013;Chapman et al., 2007;Chapman et al., 2009, 2010, Chapman and Muijs, 2013) accounts for a significant proportion of empirical studies on EH.This often utilizes a more extensive evidence base collated through a variety of studies, including work on behalf of the UK government-funded National College for School Leadership (National College) and Department for Education (DfE).Other articles make incidental reference to EH, while substantively focusing on an alternative issue.This include both articles containing limited empirical evidence on EH and more theoretical pieces.Examples of these include work relating to system leadership (e.g.Abbott et al., 2014;Cousin, 2019;Crawford et al., 2020;Greany, 2015), federations (e.g.Chapman, 2015;Chapman and Muijs, 2014), the improvement of challenging schools (e.g.Araújo, 2009), networking (e.g.Muijs et al., 2010), accountability (e.g.Ehren and Perryman, 2018) and the future of leadership more broadly (e.g.Hopkins and Higham, 2007;MacBeath, 2011).
Non-peer-reviewed studies.The most significant empirical studies focused specifically on EH do not generally feature in academic journals, but instead are published directly by relevant stakeholder organizations for English schools, most notably Office for Standards in Education (Ofsted), National College and the National Governors Association (NGA).
Of these, the National College was the most prolific producer of research into EH.Its outputs include research and guidance produced by its own staff (Barnes et al., 2005;Ireson, 2011;National College, 2014a, 2014b), serving school leaders sponsored through its Research Associates programme (Blackburn, 2012;Hummerstone, 2012) and research commissioned from academics and consultants (Chapman et al., 2007;National College, 2010).The last of these studies, completed in conjunction with the Hay Group, remains one the most robust and comprehensive studies into EH, comprising a series of surveys intended to map the scale of this phenomenon nationally, and interviews with serving executive heads themselves and associated stakeholders to understand further the principal issues.
Ofsted's (2011) study is the most extensive in terms of school visits, interviews and observations.This sampled 61 schools in 29 federations nationally, and also drew upon inspection results during their time in their federation.
While both National College's (2010) and Ofsted's (2011) studies date from the early years of federations, joint research by the NGA and NFER (Fellows, 2016;Fellows and Odell, 2016;Lord et al., 2016) is more recent in nature.It also includes the first recorded attempt to map the scale of EH through a detailed interrogation of DfE's Schools Workforce Census and Edubase databases.
RO2: What are the main findings from research completed into EH?
A thematic analysis of the material published on EH found that evidence coalesces around the following themes: 1. Defining EH and assessing its prevalence within the school system.2. The antecedents of the EH role and factors which have driven its growth.3. The focus for the EH role.4. The characteristics, skills and attributes required by EH. 5. Motivations for becoming an EH. 6.The implications of EH for governance.7. The challenges associated with EH. 8. Support EH require.9.The impact of EH.
The next section explores each of these in more depth.
Defining EH and assessing its prevalence within the school system.Unlike headship, EH lacks a legally recognized definition (Hummerstone, 2012;Lord et al., 2016) and is used inconsistently and imprecizely within the literature (Chapman, 2015).Most commonly it relates to an individual leading more than one school (Fellows and Odell, 2016) although this may or may not involve formal federation arrangements (Higham and Hopkins, 2007) (Earley et al. (2009) term this as 'federated heads').Equally such arrangements may or may not be permanent in nature (Lord et al., 2016).Furthermore, several, more recent, studies position EH as either a new middle tier within MAT structures or even as the actual MAT CEO themselves (Baxter and Floyd, 2019;Hughes, 2020).While highlighting important parallels between these alternative roles (for instance concerning focus, skills and audience), these studies also illustrate the dangers of failing to recognize two decades of structural changes which have altered the context within which all headteachers (including EH) operate, since EH first emerged 20 years ago.
Given this lack of consensus, it is unsurprising that there is no agreement as to its prevalence within the English school system.Indeed very few articles attempt to either assess its scale or give consideration to its likely prevalence in the future.Estimates which do exist generally appear in non-peer-reviewed material.The most sophisticated of these features in Lord et al. (2016) and is based on analysis of the School Workforce Census and Edubase.This calculated that in 2014, there were 621 EHTs in England, rising to 628 in 2016.However, Lord et al. (2016) note that these calculations almost certainly under-estimated the scale of this phenomenon and in particular missed many of those working as EH on a temporary basis.The significance of this under-calculation becomes more significant in light of Lord et al.'s (2016) claim that EHs are three times more likely to be appointed on a temporary basis than those in 'normal' headteacher roles, primarily due to its prevalence as a short-term intervention strategy.
In terms of profile, Lord et al. (2016) found that compared to headteachers as a group, EHs were likely to be slightly older (51 years old on average cf.49 years old for all heads), male (60% cf.56% respectively) and more likely to have higher qualifications (24% have PhDs cf.16% of all headteachers).
Many writers have identified trends which they concluded would increase the number of EHs in the coming years.Foremost amongst these were the growth in MATs (Muijs et al., 2010), the expansion of system leadership and networking (Chapman et al., 2010;Hopkins and Higham, 2007;Southworth, 2008), difficulties in recruiting headteachers (Hummerstone, 2012) and a more general diversification in leadership roles per se (Barrett-Baxendale and Burton, 2009).

The antecedents of EH.
There is a considerable discussion within the literature on the drivers behind the emergence and subsequent growth of EH.These feature particularly strongly in the peerreviewed articles in general, and are often especially well developed in more theoretically or policyfocused articles.Collectively these articles identify two separate but related themes, the confluence of which is especially important for EH.
Several writers trace the origins of EH back to the rise in New Public Management (NPM) within the education sector in the late 1980s (e.g.Tseng, 2015).Baxter and Floyd (2019) and Muijs et al. (2010) for instance highlight how the Education Reform Act 1988 precipitated a radical marketization and decentralization of schools, through the introduction of the local management of schools (LMS) and greater parental choice.Meanwhile, writers such as Hatcher (2008) note that while NPM and LMS increased the freedom and powers of an individual school, they also simultaneously reduced the influence and power of Local Education Authorities (LEA).Higham and Hopkins (2007), amongst others, highlight the widespread acceptance of NPM during the early part of the 21st century.Within the context of EH, Chapman (2015) notes how one particularly important feature in the evolution of NPM was the introduction of federations, facilitated through the Education Act 2002, which enabled up to five schools to closely collaborate with each other through the establishment of formal governance and management structures.Chapman (2015) identifies how over time, many federations utilized the flexibilities of academization to tighten the ties between individual schools, while simultaneously severing their connections with their LEA, weakening and marginalizing LEAs further.Significantly, this frequently involved introducing EH in contexts of under-performance or where resources were especially short (Hopkins and Higham, 2007).Greany and Waterhouse (2016) describe how the return of the Conservative government, initially in coalition with the Liberal party in 2011 and subsequently in its own right, further accelerated the decentralization and marketization of schools.Collectively these changes drove an unprecedented restructuring of the English schools system during the first two decades of the 20th century.Arguably this was largely ideologically and politically driven (Greany and Waterhouse, 2016), with little evidence demonstrating these changes secured genuine improvements (Chapman, 2015).
A second, parallel narrative views EH was a consequence of a radical reconceptualization of the nature of school leadership beginning with the 1988 Education Reform Act, with Tseng (2015) highlighting its significance in transforming the role of the headteacher from lead teaching professional to a position more fundamentally focused on organizational management (interestingly Hughes (1976) suggests this dates from the mid-1970s).Higham and Hopkins (2007) note how the reconceptualization of the headteacher's role was both embraced and enhanced by the new Labour government of the early 2000s, with this 'privileging' of leadership evident in many of its policies from that time (most notably the establishment in 2002 of the National College and the range of training and development opportunities promoted by it).
Core to this 'privileging' was the belief that management and leadership were essential drivers of school improvement within individual schools and the English system more broadly (Ainscow et al., 2006).An early outcome from this was the emergence of the 'superhead', where high profile headteachers were 'drafted in' to tackle underperformance in some of England's most challenging schools.While initially associated with Freshstart (Araújo, 2009), there are clear parallels between superheads and the utilization of EHs within contexts of under-performance (explored further below).However, initiatives such as Freshstart were often characterized by overly-optimist, and indeed romantic (Meindl et al., 1985) assumptions over the difference any individual leader may make to organizational success, and the ease with which 'universal' solutions to underperformance can be unproblematically transferred (Araújo, 2009).Nevertheless, over time, the acceptance of leadership as the primary driver for improvement (e.g.Day et al., 2009;Heck and Hallinger, 2004;Leithwood, 2007), coupled with a somewhat generalized approval for collaboration (e.g.Baxter and Floyd, 2019;Muijs et al., 2010) evolved into a more clearly articulated vision for a 'selfimproving system' (Greany, 2015, Hargreaves, 2010), which in turn would be driven by a new cadre of system leaders, including EH and CEOs operating within individual MATs (Hopkins, 2009).
This article provides insufficient scope for detailed discussions of the interplay between these various factors.Nevertheless, this simplified account offers insight into the fundamental changes which have affected leadership roles in English schools in the post-millennium period (Crawford and Earley, 2011), and the emergence of the EH role.
The focus for the EH role.There is remarkably little consideration given to the reasons for appointing an EH.However, where this is discussed two principal drivers can be identified.The first is essentially self-interest as a response to insufficient resourcing (e.g.Chapman and Muijs, 2013).National College (2010) found this a particularly important factor in the primary sector where shortages of headteachers were most acute and resources most stretched.National College (2014b) also identified at least one instance where an EH position was created to prevent a headteacher leaving their post.The second theme is interventionist in nature, and involves an EH appointment as part of a strategy to address underperformance (Chapman and Muijs, 2013;Higham and Hopkins, 2007).
As noted previously, no reliable data exists as to the prevalence of each in practice (Lord et al., 2016).However, while both themes feature in theoretical and empirical work, empirical evidence places greater emphasis on how practical considerations were the principal driver behind decisions to appoint an EH.This may therefore imply that discussions around the strategic imperative behind this role may be overstated.
Interestingly, a closer examination of relevant evidence highlights several similarities between the EH and MAT CEOs roles.Chapman (2013), for example, highlights how EH involves both traditional and innovative elements of headship, which are blended to meet the context-specific requirements.More broadly, most writers conceptualize EH as combining strategic and operation foci.For instance, Higham and Hopkins (2007) see these coalescing around three principal priorities of setting direction, developing people and improving organizational effectiveness.Other writers highlight tackling underperformance (Tseng, 2015), for instance through building leadership capacity, creating a positive culture, leading change and forging effective partnerships (Harris et al., 2006).Similarly, Chapman (2013) and National College (2010) note the importance of addressing underperformance amongst individual members of staff, for instance through coaching or facilitating their exit from the school.
Interestingly, Higham and Hopkins (2007) highlight how EH can also be either a short or medium-term role, and the need for clarifying expectations at the point of appointment.Specific considerations include establishing processes for accountability, improvement targets, governance arrangements and the allocation of resources.They also emphasize the need to identify a specific end date for this arrangement and to implement an appropriate exit strategy.
The characteristics, skills and attributes required by executive heads.The characteristics, skills and experience required of EH feature in around half of the materials identified.However the strength of such assessments vary, and considerations are often implicit and inferential rather than explicit and evidenced in nature.There is also marked variation in the themes identified, which in part reflects differences in the strength of the evidence underpinning them.For example, more theoretical articles are more likely to provide a higher-level, generalized view of the requirements of EH (e.g.Close, 2016;MacBeath, 2011).Some articles discuss these issues as part of their literature review or introduction rather than the main findings of the article, thereby recycling older studies rather than introducing new insight.Many contain evidence from fewer than a handful of contexts (e.g. Brown and Flood, 2018;Kulz, 2017;National College, 2014b), while others consider EH incidentally.Such findings therefore need to be treated with considerable caution.
Collectively, the review found 59 different areas of experience, expertize or personal characteristics, highlighted in the literature as important to EH.However, approaching one-half of these featured in a single source only.The most commonly mentioned areas are a mixture of personal characteristics, professional capabilities and practical experience.Foremost amongst these is the ability to build relationships with different stakeholder groups within and without the school, including parents, governors, partner organizations and school staff (e.g.Chapman, 2013;National College, 2014a;Hummerstone, 2012).Building leadership capacity also featured strongly (e.g.Blackburn, 2012;Bush and Glover, 2012;Robinson, 2011) alongside the ability to promote the professional development of school staff (Chapman and Muijs, 2014;Ofsted, 2011).
The personal attribute most commonly highlighted was resilience, which reflects the complex and demanding nature of the role (e.g.Abbott and Bush, 2013;Hargreaves and Harris, 2015;Higham and Hopkins, 2007).Associated themes were persistence, commitment and personal courage (e.g.Chapman et al., 2010;Courtney and Gunter, 2015).Similarly, a clear sense of moral purpose is also commonly highlighted as essential, alongside the ability to both demonstrate and demand this of others (e.g.Fellows, 2016;Hopkins and Higham, 2007;Kulz, 2017).
As expected, a variety of leadership-related themes feature strongly in the review.While these vary in terms of specificity, there is some sense that being an effective EH demands more than 'simply' being a good school leader (e.g.Chapman, 2015;Howland, 2015).Tseng (2015) for instance suggests it demands leadership skills more commonly associated with the private sector than education, most notably strategic thinking, a quality also highlighted within many of the most extensive studies (e.g.Barnes, 2006;Fellows, 2016;Hummerstone, 2012;National College, 2014a).
Motivations for becoming an executive head.Evidence on motivations for becoming an executive head identifies both intrinsic and extrinsic factors.
The most prevalent of these is a sense of public duty.Blackburn (2012) for instance notes a sense of 'overwhelming moral imperative', while Cousin (2019) highlights a commitment to contribute and make a difference more broadly.National College (2010) and Chapman et al. (2010) also emphasize a desire amongst EH's to impact on the learning and life chances of pupils beyond their own school.A second intrinsic motivation is the opportunity to pursue a new challenge (Cousin, 2019;Robinson, 2011).Finally, National College (2010) highlights how some EH found the position brought validation to them as professionals.
Extrinsic motivators concern status and career progression.Hummerstone (2012) for instance sees EH as the zenith of a leader's career and concludes that this should be reflected in the level of status and reward associated with it.Similarly, Cousin (2019) and Chapman (2013) highlight the significant autonomy, status and pay associated with the role, including opportunities to inform policy.EH can also provide valuable learning and professional development.Chapman (2015Chapman ( , 2013) ) for instance flags how leaders value opportunities to work across schools and learn from other's practices.Meanwhile, Lord et al. (2016) note how it requires the development of new skills.
The implications of EH for governance.The governance of EH features in more than one-third of articles identified as relevant to this review.Collectively these agree that no preferred model exists for governance in contexts involving an EH (Fellows, 2016;National College, 2014b;Ofsted, 2011).Instead, governance structures should reflect the needs of the schools involved and the rationale for adopting EH (Ofsted, 2011).Chapman and Muijs (2014) for instance identified six variables that inform the rationale for and nature of a federation, and influence the construction and operation of governance structures utilized.These include phase, level of performance, size and extent of academization.Simkins et al. (2019) also note how phase influences governance structures in contexts with an EH, while Baxter and Wise (2013) and Chapman et al. (2010) identify the move to a hard federation as the single biggest driver of structural change.
While advocating flexibility, several writers nevertheless seek to better understand how different structures can be employed.For instance, National College (2014a, 2014b) highlights the effective utilization of school committees while Chapman and Muijs (2013) conclude that shared governance arrangements are the most commonly adopted model in EH contexts.Similarly, Lord et al. (2016) identify four principal models which are adopted in practice in these situations, comprising: 1. EH reporting to one governing board which manages the whole network.2. EH reporting to a governing board of trustees for the whole trust, and governing committee for individual schools.3. EH reporting to multiple governing boards, representing each individual school.4. EH being managed by the 'executive' branch, for example, CEO or director.
Collectively, this wide variety in approaches results in a system characterized as complex and opaque (Baxter and Wise, 2013;Courtney and Gunter, 2015;Ehren and Godfrey, 2017), with variations in contracts (Lord et al., 2016) and alternative levels of autonomy (Ehren and Perryman, 2018;Greany and Waterhouse, 2016).Meanwhile, differences in MAT arrangements add further confusion (National College, 2014a).Unsurprisingly, Higham and Hopkins (2007) highlight the need for further guidance on the effectiveness of alternative approaches.
Underpinning discussions on the form structures should take are several specific considerations governors must address.Firstly, the presence of an EH inevitably demands trade-offs between school-specific and wider priorities (e.g.Hatcher, 2014Hatcher, , 2008)).Secondly, all structures have implications for the power and autonomy of the EH (Chapman, 2013;Hatcher, 2008Hatcher, , 2014)).Finally, these need to be offset against their effectiveness in holding the EH to account (Abbott et al., 2014).
Collectively these issues have significant implications for the skills and capabilities of individual governors and EHs themselves.National College (2014a) for instance highlights how increased autonomy associated with federations (in which EH commonly operate) demands greater levels of specialization and business acumen from governors and advocate the development of 'specialist' governors with specific expertise in law, finance, marketing and HR (NB support in these technical areas would historically have been offered by the LA).Elsewhere, Robinson (2011) notes how the complexity of arrangements increases the need for EH to work closely with, and effectively manage, their governing body if they are to successfully perform their role.
Challenges facing executive heads.Numerous difficulties are identified within the literature, albeit from a relatively small number of studies.Challenges themselves fall into three principal areas: 1. Challenges relating specifically to the role of the executive head 2. Challenges relating to the utilization of system leaders more generally 3. Challenges affecting federations in general.
Each of these is considered further in Table 1.
Support and development required by executive heads.Scant consideration is given in the literature to the support required by executive heads.Indeed it is largely ignored in both theoretical and smaller-scale empirical papers and only considered in some of the most significant research projects sponsored by NGA (Lord et al., 2016), National College (2010) and Ofsted (2011).It also features in the work by Chapman (2015).These studies agree that little support has been available for those in or aspiring to EH positions (Lord et al., 2016;Ofsted, 2011).Moving forward three specific areas of focus are identified.Firstly, EH's are anticipated to benefit from training in several job-specific roles, including strategic thinking, 'technical behaviour' and interpersonal skills (National College, 2010).The precise nature of this support should be flexible enough to reflect variations in EHs' contexts (Lord et al., 2016;Ofsted, 2011).Secondly, peer-to-peer support is viewed as critical, and best facilitated through mentoring (National College, 2010) and sharing good practice (Ofsted, 2011).Thirdly, Chapman (2013) advocates a wider discussion on the expectations of EH and challenges assumptions of heroic leadership which underpin it.In doing so he proposes EH be reconceptualized as a team rather than individual responsibility, thereby increasing its capacity and sustainability.
The impact of executive headship.Relatively little consistent evidence exists on the impact of EHs (Chapman et al., 2007;Fellows and Odell, 2016;Harris and Townsend, 2007;Lord et al., 2016;Muijs et al., 2010;National College, 2010).Interestingly, several authors observe that this may not be entirely unexpected.For instance, Wettenhall (2013) notes that the public reform 'industry' is frequently not evidence-based.Elsewhere, Chapman (2015) opines that insufficient effort has been made to gather the evidence required to justify the significant policy-driven structural changes that have affected schools since the mid-2000s.Equally, Greany and Waterhouse (2016) conclude that too many changes in school are politically and ideologically driven.From an alternative perspective, evidence emphasizes how EH can facilitate the pooling of resources (Chapman, 2015;National College, 2014a;Ofsted, 2011) and sharing best practices across schools (Howland, 2015;Muijs et al., 2010) including pedagogy (Muijs et al., 2010;Ofsted, 2011) and leadership development (National College, 2010).Chapman (2015) also notes that federations more broadly can increase the scale and scope of the provision, and that this is most likely to occur where EHs are in place.
The strongest evidence that EH impacts on pupil outcomes comes from Chapman and Muijs (2013).This found federations reduce variation in pupil outcomes by 7-34%, 2 years after federating, with improvements at the higher end of this range most likely to occur in instances where an EH is in place.Chapman (2015) also highlights evidence of wider impacts on pupils from federations, which again, is most likely to occur in contexts where an EH is in place.These relate to behaviour, pupil enjoyment, pastoral support (Ofsted, 2011), transition (Chapman, 2015;Ofsted, 2011), general wellbeing (Chapman, 2015) and wider social benefits (National College, 2014b;Ofsted, 2011).
Disappointingly, very little evidence exists on factors that support the success of EH.Indeed this features in only three articles.The most extensive examination is provided by National College (2010) which concludes that prior collaboration, leadership capacity in the EH's 'home school' and completing a process of due diligence were all indicators of likely success.National College (2014b) notes that ongoing support for the EH is also important.Higham and Hopkins (2007) identify similar themes, emphasizing ensuring clarity on the priorities for the role (including clearly establishing the programme for improvement), and ground rules on how EH operates in intervention-based contexts.They also prioritize the need to commit to an end date for the arrangement and to establish a clear exit strategy for this.

Discussion
What are the implications of this evidence, for practice, policy and future research?(RO3) In the 20 years since its emergence, EH has become a well-established school leadership role in its own right.While estimates vary, a significant number of EHs are now in post and collectively their reach is approaching or in the region of that for special school headteachers.
Nevertheless, the phenomenon of EH remains largely unexplored.While EH features in many peer-reviewed journal articles, these commonly examined it from either a largely theoretical perspective or as an aside from their principal focus, for instance, federations or system leadership.
Equally where empirical studies are reported these are generally small-scale and lack wider applicability.Instead, findings from the few larger-scale studies in this field are commonly published by their commissioning body and not subject to peer review (work by Chapman et al., being a notable exception to this).Consequently, while we know much about the policy and philosophical drivers behind the emergence of this role, markedly less is understood of its strengths and limitations, what it demands of leaders in practice or the nature of support they require.
Several important implications therefore stem from this review.Firstly, research is needed to address the various gaps in evidence identified in this article.In particular, far more is required on the practice of EH and the qualities it demands of those who perform this role.At the same time, more accurate data is needed to understand both the number of executive heads currently in the schools system and how its prevalence may grow in the coming years, to facilitate the planning and delivery of support required.
As part of this, additional work is also needed to clarify how executive heads can be used most impactfully in practice.This is essential if the true potential of this strategy is to be realizedthat is, not only as a response to operational imperatives but also as a genuine long-term strategy for driving school improvement.Indeed this article has demonstrated that while limited in scale, there is nevertheless evidence to show that by facilitating the sharing of good practice, EH can have a marked impact on attainment by reducing variation in pupil outcomes.At the same time, EH can significantly contribute to wider school improvement in a variety of other ways, including measures to improve the wider experience of students (for instance during transition), providing strategic direction, improving organizational culture and managing resources.Moving forward, such insight should provide the foundation for policy and guidance on how best to utilize EH in a more systematic and coordinated fashion than has previously been the case.
As noted earlier, the English school system has undergone unprecedented restructuring since EH first emerged in the early 2000s.One consequence of this has been the emergence of a new cadre of school leaders in the form of MAT CEOs.While the nature of (and responsibility associated with) this role may vary greatly, there are nevertheless areas where distinct parallels between EH and MAT CEOs can be identified.Indeed, and as noted, in some contexts these terms are used interchangeably.There is, therefore, merit in examining further ways in which EH may provide invaluable support in developing MAT CEOs of the future.
While this study focused on the English context, it is important to recognize that variations on the EH theme also exist in other countries, most notably the superintendent/principal supervisor role in the USA.Examining the learning from these models is therefore important in informing the development and deployment of EH in the future.For instance, Honig and Rainey (2019) found that such supervisors impact on pupil outcomes is increased by supporting and promoting teaching and learning, rather than focusing on compliance, performance management or operational issues.Elsewhere Goldring et al. (2018) found principals benefit particularly from job-embedded, coaching support from an experienced colleague, such as an EH.More broadly, work by Leithwood (2019) suggests that EH may be able to make an important contribution to building leadership capacity through greater involvement in leadership networks, both by directly sharing their personal knowledge, experience and expertize, but also through their potential to act as a facilitator and driver of the network itself.Collectively, such findings may provide valuable insight into how EH can be more consistently and effectively utilized in England to increase school effectiveness.
Finally, the implications of EH for models of accountability remain opaque.Few studies have explicitly considered the most effective ways of addressing this and, where they have, too often their findings on which strategies to adopt have been vague.Greater clarity is required as to the relative strengths and weaknesses of alternative accountability approaches in practice, if governors are to make more informed decisions about whether and how to implement this strategy in their schools.