Formative assessment_ A systematic review of critical teacher prerequisites for classroom practice

Formative assessment has the potential to support teaching and learning in the classroom. This study reviewed the literature on formative assessment to identify prerequisites for effective use of formative assessment by teachers. The review sought to address the following research question: What teacher prerequisites need to be in place for using formative assessment in their classroom practice? The review was conducted using a systematic approach. A total of 54 studies were included in this review. The results show that (1) knowledge and skills (e.g., data literacy), (2), psychological factors (e.g., social pressure), and (3) social factors (e.g., collaboration) influence the use of formative assessment. The prerequisites identified can inform professional development initiatives regarding formative assessment, as well as teacher education programs.


Introduction
Using assessment for a formative purpose is intended to guide students' learning processes and improve students' learning outcomes (Van der Kleij, Vermeulen, Schildkamp, & Eggen, 2015;Bennett, 2011;Black & Wiliam, 1998). Based on its promising potential for enhancing student learning (Black & Wiliam, 1998), formative assessment has become a "policy pillar of educational significance" (Van der Kleij, Cumming, & Looney, 2018, p. 620). Although there is still no clear consensus on what the term "formative assessment" encompasses ( Van der Kleij et al., 2015;Bennett, 2011;Torrance, 2012;Wiliam, 2011), it is broadly accepted as a good classroom practice for teachers (Torrance, 2012). Drummond, 2006;Swaffield, 2011). A key conclusion of several reviews of formative assessment (Black & Wiliam, 1998;Torrance, 2012) is that how teachers implement formative assessment is critical for its potential to enhance student learning. Teachers thus play a crucial role in formative assessment. However, the guidance available to teachers is often limited to generic principles ( Van der Kleij et al., 2018;Elwood, 2006), or at times even inappropriate (Van der Kleij et al., 2018), resulting in limited use of formative assessment in practice (Torrance, 2012).
One of the problems in implementation of formative assessment is that often only certain 'principles' of formative assessment have been adopted, without much consideration of the broader implications for classroom practice (Elwood, 2006;Torrance, 2012). Formative assessment is not an add-on activity, but rather needs to be an integrated element of instruction, which requires a fundamental change in the role of the teacher in the classroom. It also requires a fundamental shift in the power relations between teachers and students, in which teachers and students become jointly responsible for the quality of teaching and learning in the classroom (Black & Wiliam, 1998).
It is still unknown what the requirements are for teachers to use formative assessment effectively in their classroom practice. Although several theoretical models have provided insights into what factors may be of importance (e.g., Heritage, 2007;Mandinach & Gummer, 2016), these models (1) focus on either AfL or DBDM approaches to formative assessment, and (2) are only partially based on empirical evidence. This study aims to address this gap, by reviewing the available evidence from the literature about prerequisites for teachers' use of formative assessment. This review sought to address the following research question: What teacher prerequisites need to be in place for using formative assessment in their classroom practice?

Procedure
This review was part of a larger project, which aimed to identify prerequisites for formative assessment in classroom practice (Schildkamp, Heitink et al., 2014). The review used the methods for conducting systematic literature reviews in the social sciences described by Petticrew and Roberts (2006). After formulating our research question, we defined our search terms, selected literature databases, and started searching for publications. A library expert was consulted during the literature search process. Next, we formulated inclusion criteria, which formed the basis for selecting relevant publications. All relevant publications were read in full and a purposefully developed data extraction form was constructed to enable comparison of the same units of information from each selected publication. Finally, the results from publications judged to be of sufficient quality were synthesized to answer the research question.

Databases and search terms
Five databases (Education Resources Information Center [ERIC], Web of Science, Scopus, PsychINFO and Picarta) were systematically searched (early 2014) using the same search terms. Initial search terms included 'formative assessment', 'data-based decision making', 'assessment for learning', and related terms as found in a thesaurus and/or terms that were used in other relevant publications. To narrow down the results to publications relevant to formative assessment, the term 'feedback' was added to the search string. The search was further narrowed down by adding the term 'classroom' and related terms to the search string. The retrieved publications were exported to Endnote X6 for systematic selection using the inclusion criteria.
The reliability of the data extraction process was safeguarded by having two researchers independently code approximately 50 % of the selected publications. Agreement rates of 80 % and a Cohen's Kappa of .620, demonstrated satisfactory inter-coder reliability (Landis & Koch, 1977). Each of the selected publications was scored on 11 quality criteria (see Schildkamp, Heitink et al., 2014). A score of 0, 0.5 or 1 was assigned to each criterion. As we wanted to base this review on high-quality studies only, a publication had to score an average of 7 or higher to be included. Publications with a score between 5 and 7 were discussed between at least two researchers, and publications with a score lower than 5 were excluded. When a study was coded by multiple researchers, the average of the quality score was taken.

Data analysis
The results were organized around three categories of prerequisites established inductively from the reviewed studies. This process of organizing the data around these categories of prerequisites was discussed with multiple researchers, to overcome the bias that can develop when only one researcher does the process of analysis (Poortman & Schildkamp, 2011;Green, Johnson, & Adams, 2006). We identified the following three categories of teacher prerequisites, which all influence each other: (1) knowledge and skills, (2) psychological factors, and (3) social factors, see Fig. 1.

Search and selection results
An overview of the search process and results in the form of a PRISMA diagram (Moher, Liberati, Tetzlaff, & Altman, 2009) is provided in Fig. 2.
At the end of the literature identification process, 200 publications were deemed suitable for data extraction. However, screening of the publications led to the realization that we had missed publications in the field of DBDM. For this reason, we conducted an additional DBDM-specific search. This search was conducted without 'feedback' in the search string, as experts in the field had indicated that this specific term is often not used.
A total of 256 publications that were available in full text were screened for relevance using the inclusion criteria. In this screening stage, it was concluded that 125 publications did not meet the inclusion criteria after all (for example, because they focused on the use of data by school leaders or on evaluations at the school level). This left a total of 131 publications suitable for data extraction. Based on the data extraction, 77 publications were either found to be of insufficient quality or lacked too much information from the method section to judge the quality of the study. These publications were removed from the selection. The remaining 54 publications were included in this review (see Table 1).

Characteristics of selected studies
The selected publications were classified as focusing on either DBDM or AfL. When studies involved a mix of DBDM and AfL, they were classified according to the dominant approach. A total of 29 studies focused on DBDM (e.g., the use of standardized tests, the use of self-evaluation results, and the use of evidence from systematic observations). The DBDM studies were predominantly conducted in primary education (n = 22). Most of these studies were conducted in the US (n = 16) and most were of a qualitative nature (n = 18). The 25 AfL studies focused on different types of assessment occasions, ranging from discussions in the classroom to formal types of assessment such as paper-and-pencil tests. AfL studies were conducted in both primary education (n = 14) and/or secondary education (n = 17). Most AfL studies used either a qualitative design (n = 12) or a mixed method design (n = 9) (see Table 2 for more information). K. Schildkamp, et al. International Journal of Educational Research 103 (2020) Table 3 presents an overview of the studies that investigated specific influential factors related to the role of the teacher (see Table 2). When interpreting these results, it is important to consider that just because certain factors have been studied more than others, that does not imply that these factors are more important.
Data literacy and assessment literacy also include the knowledge and skills to analyze and interpret different types of data, such as assessment evidence and classroom observations Kerr et al., 2006;Lee et al., 2012;Levin & Datnow, 2012;Schildkamp & Kuiper, 2010;Schildkamp & Visscher, 2010a;Schildkamp et al., 2012;Schildkamp, Karbautzki et al., 2014, 2010bVan der Kleij & Eggen, 2013;Young, 2006). Van der Kleij and Eggen (2013), for example, found that some teachers do not possess the basic skills needed to interpret score reports from a pupil monitoring system in primary education. If teachers do not know how to analyze and interpret the collected data, this will lead to a lack of or even inappropriate (e.g., providing students with inaccurate feedback) use of formative assessment.

Table 3
Overview of studies that investigated influential factors.

Pedagogical content knowledge
Fifteen studies concluded that teachers need pedagogical content knowledge (PCK) to be able to implement DBDM or AfL (Aschbacher & Alonzo, 2006;Birenbaum et al., 2011;Blanc et al., 2010;Feldman & Capobianco, 2008;Fletcher & Shaw, 2012;Fox-Turnbull, 2006;Fuchs et al., 1999;Gottheiner & Siegel, 2012;Harris, Brown, & Harnett, 2014;Kay & Knaack, 2009;Lee, 2011;McNaughton et al., 2012;Penuel et al., 2007;Yin et al., 2013). PCK refers to subject-matter content knowledge, as well as knowledge about how to teach subject-matter knowledge. Assessment evidence can help teachers to identify students' misconceptions. Teachers then need PCK to determine how to provide feedback to students and/or alter their instruction. Gottheiner and Siegel (2012), for example, found that teachers must have knowledge of common misconceptions within the subject. Aschbacher and Alonzo (2006) found that without sufficient content knowledge, teachers are not able to provide students with accurate and complete feedback on their learning and achievement.

Goal setting
Several studies found that goal setting can promote the use of DBDM or AfL (Birenbaum et al., 2011;Hargreaves, 2013;Havnes, Smith, Dysthe, & Ludvigsen, 2012;Levin & Datnow, 2012;Newby & Winterbottom, 2011;Penuel et al., 2007;Peterson & Irving, 2008;Schildkamp & Kuiper, 2010;Schildkamp et al., 2012;Schildkamp, Karbautzki et al., 2014, 2010bVanhoof, Verhaeghe, Van Petegem, & Valcke, 2012). In the case of DBDM, this can refer to goals at the level of the school, the classroom, or the individual student. In the case of AfL, the focus is on student learning goals. When the goals are clear and measurable for both teachers and students, (assessment) data can provide teachers and students with feedback on their progress with regard to these goals (Schildkamp & Kuiper, 2010;Schildkamp et al., 2012;Schildkamp, Karbautzki et al., 2014, 2010b. Peterson and Irving (2008) found that it is important that teachers and students formulate individual student learning goals together. According to these researchers, this encourages students to reflect and act on feedback.
• Type of feedback: Teachers can provide feedback in terms of performance, effort, or achievement (Gamlem & Smith, 2013). With regard to providing students with feedback on their achievement in the form of grades, Peterson and Irving (2008) found that providing students with a grade was essential for their motivation. However, Lee (2011) found that giving grades negatively influenced students' willingness to take risks and learn new things. Birenbaum et al. (2011) also found that a focus on assigning grades and preparing for tests can hinder AfL. Teachers can also provide students with process feedback, focused on strategies to bridge the gap between where students are and where they need to be (Gamlem & Smith, 2013;Havnes et al., 2012;Lee, 2011;Peterson & Irving, 2008). Such strategies may be explicit or more implicit, for example, in the form of cues (Gamlem & Smith, 2013;Hargreaves, 2013;Rakoczy et al., 2008).

Facilitating classroom discussions
Another factor not found in the DBDM literature, but stressed in the AfL literature, is that teachers need to be able to facilitate classroom discussions. This includes teacher questioning to elicit evidence about student learning (Aschbacher & Alonzo, 2006;Feldman & Capobianco, 2008;Fox-Turnbull, 2006;Furtak & Ruiz-Primo, 2008;Gottheiner & Siegel, 2012;Gamlem & Smith, 2013;Hargreaves, 2013;Havnes et al., 2012;Lee et al., 2012;Penuel et al., 2007;Ruiz-Primo & Furtak, 2006). For example, Furtak and Ruiz-Primo (2008) found that it is important that teachers are able to ask the right questions at the right time (planned and unplanned formative assessment). Ruiz-Primo and Furtak (2006) found that it is important that teachers ask 'why/how' questions to get more information about student understanding. They found that discussions with students help to make students' levels of knowledge explicit. Havnes et al. (2012) called these "mutual learning dialogues" (p. 26).

ICT skills
The use of DBDM increasingly requires ICT skills as found in several studies, for example, regarding how to use information management systems and assessment systems Staman, Visscher, & Luyten, 2014), and/or performance feedback tools, such as school self-evaluation systems (Schildkamp & Teddlie, 2008;, 2010b. AfL also requires certain ICT skills as indicated in four studies, for example, with regard to how to use certain digital assessment systems and tools (

Involving students
Only one study discussed the importance of involving students in DBDM. Kennedy and Datnow (2011) focused on discussing assessment results with students, and concluded that most schools do not involve students in the use of data. However, students were involved in the analysis of their test scores in some exemplary schools.
Several studies pointed to the importance of involving students in AfL (Fletcher & Shaw, 2012;Havnes et al., 2012;Rakoczy et al., 2008). Harris and Brown (2013) found that good classroom relations between teachers and students are essential, and making mistakes should be viewed as an opportunity to learn by both teachers and students. Fletcher and Shaw (2012) suggested that teachers can involve students in the process of AfL by giving them specific responsibilities, for example, by letting students set their own learning goals and learning paths. According to Havnes et al. (2012), students appreciated such involvement in their own learning.
Several studies focused on peer-and self-assessment as a way of involving students (Bryant & Carless, 2010;Gamlem & Smith, 2013;Harris & Brown, 2013;Kay & Knaack, 2009;Lee, 2011;Newby & Winterbottom, 2011;O'Loughlin, Ní Chróinín, & O'Grady, 2013). Bryant and Carless (2010) emphasized the importance of the teacher knowledge and skills required for using peer-and selfassessment. Harris and Brown (2013) found that it is important that teachers explicitly articulate a rationale for the use of peer-and self-assessments, and communicate this with students. Further, teachers need to provide students with peer-and self-assessment criteria and help students in applying these. The effective use of peer assessment also requires that teachers teach students how to provide useful feedback (Newby & Winterbottom, 2011).
In contrast, a positive attitude can enable the use of DBDM or AfL. Birenbaum et al. (2011), Penuel et al. (2007), Rakoczy et al. (2008), and Sach (2013 found that a more constructivist teacher stance (e.g., students should become autonomous and are capable of learning on their own) can enable formative assessment use. Furthermore, buy-in and belief in the use of data are important. Teachers should believe that the use of data can improve the quality of their classroom practice (Jimerson, 2014;Kerr et al., 2006;Schildkamp & Kuiper, 2010;Schildkamp et al., 2012;Schildkamp, Karbautzki et al., 2014, 2010bVan der Kleij & Eggen, 2013;Vanhoof et al., 2012;. A positive attitude also implies that teachers are not afraid to make changes based on data (Schildkamp & Teddlie, 2008;, 2010b.

Ownership
Ownership over assessment results and student learning can also influence DBDM or AfL implementation. The degree to which teachers feel that they have autonomy to make decisions relates to the ownership they feel over assessment results. Low self-efficacy and lack of ownership (e.g., the quality of my teaching is not reflected in the students' assessment results) can hinder DBDM or AfL (Aschbacher & Alonzo, 2006;Datnow et al., 2013;Levin & Datnow, 2012;Sach, 2013;Schildkamp & Kuiper, 2010;Schildkamp & K. Schildkamp, et al. International Journal of Educational Research 103 (2020) 101602 Visscher Schildkamp et al., 2012;Schildkamp, Karbautzki et al., 2014, 2010b. Teachers need to feel that they are responsible for student learning and achievement in their school, and not just for covering the curriculum (Aschbacher & Alonzo, 2006;Sach, 2013).

Social pressure and perceived control
Social pressure is related to perceived control and autonomy. Several DBDM studies found that a certain amount of social pressure can enable the use of DBDM (Schildkamp & Kuiper, 2010;Schildkamp & Teddlie, 2008;Schildkamp & Visscher, 2010b;Schildkamp et al., 2012). In these cases, social pressure by means of encouragement from the principal enabled the use of DBDM. Sometimes a lot of social pressure, for example, from the accountability system, limits the perceived control that teachers feel they have. Teachers need to feel that they have sufficient autonomy to make changes in instruction and the curriculum based on data, in DBDM (Kerr et al., 2006;Schildkamp & Kuiper, 2010;Schildkamp & Teddlie, 2008;Schildkamp & Visscher, 2010b;Schildkamp et al., 2012) and AfL (Birenbaum et al., 2011;Sach, 2013). Schildkamp and Teddlie (2008), for example, found that the degree of autonomy (e.g., the extent to which teachers feel that they can take measures based on the data) influenced teachers' data use.
In several DBDM studies, teachers indicated they were only using data because they felt forced to do so or felt pressured by the accountability system (e.g., social pressure), and not because they believed data use to be important for improving classroom practice (Hubbard et al., 2014;Jimerson, 2014;Schildkamp & Teddlie, 2008;, 2010bSutherland, 2004). In two AfL studies (Aschbacher & Alonzo, 2006;Lee et al., 2012) it was also found that teachers felt pressured by the accountability system. In the DBDM studies, data use was often linked to accountability and high stakes testing, and not to improvement (Hubbard et al., 2014;Jimerson, 2014;Schildkamp & Teddlie, 2008;, 2010bSutherland, 2004). For example, Sutherland (2004) concluded that data use is sometimes seen as something that is done to the school instead of done by and for the school. A study by Hubbard et al. (2014) showed that educators were likely to use data only in subjects in which there are regular benchmark assessments for accountability purposes, such as language and mathematics. Furthermore, too much social pressure sometimes led to overly prescriptive feedback, where the students were required to directly copy information from the blackboard (Aschbacher & Alonzo, 2006). Lee et al. (2012) found that teachers sometimes felt pressured by curricular constraints, which hindered their use of AfL.

Discussion
As noted previously, the DBDM and AfL approaches to formative assessment (Van der Kleij et al., 2015) differ with respect to the types of assessment instruments used, the frequency with which they are applied in the classroom, and their relevance at various stages in the learning process. As a result, these two formative assessment approaches require different things from teachers. To address these differences, this review distinguishes between DBDM and AfL when reviewing evidence about critical prerequisites for the teachers' role in formative assessment.

The role of the teacher in formative assessment
Formative assessment (DBDM and AfL) is not just about the evidence collected; it is mostly about how this evidence is used by teachers and students to influence student learning. As concluded by Black and Wiliam (1998), the teacher plays a fundamental role in formative assessment, and formative assessment can only lead to increased student learning if it is adequately implemented by teachers. In other words, formative assessment is only as effective as the teacher who implements it (Evans, 2009). Therefore, our main research question was: What teacher prerequisites need to be in place for using formative assessment in their classroom practice?
In this review, various prerequisites related to knowledge and skills, psychological factors and social factors were found to influence the use of formative assessment by teachers. Based on the results, Fig. 3 illustrates a conceptual model displaying the various prerequisite categories and their hypothesized relations with each other. For example, teachers with a negative attitude towards formative assessment (psychological factor) are not likely to work on their data and assessment literacy (knowledge and skills). Teachers who collaborate with other teachers and students (social factor) are likely to learn from such interactions (knowledge and skills).

Data literacy
Regarding teachers' knowledge and skills, important factors are adequate levels of data literacy, assessment literacy, pedagogical content knowledge, skills with regard to goal setting, providing feedback, facilitating classroom discussion, and ICT skills. Although discussed as separate skills in this review, several of these skills can be combined in the overarching meta-construct of data literacy (Beck & Nunnaley, 2020;Mandinach & Gummer, 2011. Data literacy consists of several subconstructs, as identified by Mandinach and Gummer in their data literacy framework (2011,2013,2016). These subconstructs include assessment literacy, pedagogical content knowledge, goal setting, providing feedback, collecting different types of data (including moment-to-moment data, such as information collected based on classroom discussion), as well as the ICT skills needed to store, collect, and analyze data (Beck & Nunnaley, 2020;Mandinach & Gummer, 2011. Pedagogical content knowledge was found to play an important role, for both DBDM and AfL, as it enables teachers to contextualize data within the content domain and its learning stages. Teachers need to understand what the data mean in relation to the goals, K. Schildkamp, et al. International Journal of Educational Research 103 (2020) 101602 learning objectives and criteria for success of the content domains. Then, they can determine what instructional steps to take or what feedback to provide. For teachers to be able to determine the next instructional steps, it is important that they have set clear goals. This is an important subconstruct in the Mandinach and Gummer (2011 data literacy framework, as well as the first aspect of the data literacy continuum developed by Beck and Nunnaley (2020). Teachers should share learning objectives and criteria for success with students during the lesson, so that both students and teachers are aware of the learning goals, and how it will be determined whether students have achieved these goals. Moreover, the AfL literature has emphasized the need to involve students in developing their own goals and criteria for success (Black & Wiliam, 2009;Wiliam & Leahy, 2015). Although it did not emerge as a finding from the empirical literature in this review, several authors have highlighted the importance of involving students in setting their own learning goals in DBDM (e.g., Hamilton et al., 2009).
Data literacy (Beck & Nunnaley, 2020;Mandinach & Gummer, 2011 also involves collecting, managing, and organizing a variety of high-quality data. For example, Mandinach and Gummer's literacy framework (2011 includes the ability of educators to collect and organize a wide variety of data; not only assessment data, but also data such as behavioral and affective data, in order to more holistically analyze academic growth at the student, classroom, and school levels. As emphasized in the AfL literature, this also includes collecting data by means of facilitating classroom discussions. For example, teachers can ask openended questions that require students to think critically. Answers to these questions will provide in-depth information on student learning, which teachers can use formatively (Wiliam & Leahy, 2015).
Furthermore, it is essential that the collected data are analyzed (turning data into information) and transformed into decisions (Beck & Nunnaley, 2020;Mandinach & Gummer, 2011, so that teachers can provide feedback to students. For example, feedback can suggest to students how to move their learning forward (Van der Kleij et al., 2015;Sadler, 1989).
Finally, data literacy includes ICT skills (Beck & Nunnaley, 2020;Mandinach & Gummer, 2011, such as knowing how to work with digital assessment and data systems. However, we want to stress here that although data availability and access may be facilitated by some sort of data or assessment system, it is crucial that these data are perceived as relevant, reliable, and valid by teachers . Moreover, ICT skills are an important condition, but they are not sufficient to ensure actual data use in schools on their own (Cho, Allwarden, & Wayman, 2016;Hamilton et al., 2009;.

Social factors
Social factors also play a role in teachers' use of formative assessment. Relationships between teachers, as well as between teachers and their students, are vital. These relationships, or social networks, are important because they facilitate the exchange of resources such as information, knowledge, and advice (Daly, 2010). Collaboration with colleagues is an important prerequisite for teachers' use of formative assessment, for example, through engaging in discussions regarding how to improve classroom practices based on assessment results. Relationships between teachers and students also play an important role in AfL. For example, teachers can involve students by involving them in the process of formative assessment by using forms of peer-and self-assessment in the classroom. This can lead to increased self-regulation and improved learning outcomes (Black & Wiliam, 2009;Wiliam & Leahy, 2015). Although limited empirical evidence was found for involving students in DBDM, some publications (e.g., Hamilton et al., 2009) did emphasize the importance of involving students in DBDM, for example, by teaching students to examine their own data. K. Schildkamp, et al. International Journal of Educational Research 103 (2020) 101602

Psychological factors
Finally, the following psychological factors can enable teacher use of formative assessment in the classroom. First, it is important that teachers have a positive attitude toward the use of formative assessment, and believe that formative assessment can make a difference to their classroom practice and student learning. Second, the degree to which teachers feel ownership over the process and results of formative assessment matters. Furthermore, social pressure plays a role. When teachers feel too much (accountability) pressure from their district leaders, for example, this may hinder their use of formative assessment. If there is too much social pressure, the focus is often on summative assessment and meeting certain benchmarks. However, a certain degree of social pressure, for example, pressure from the principal to use data, can actually enable the use of formative assessment. Finally, it is important that teachers perceive control over what happens in the classroom. They need to feel that they have sufficient autonomy to make decisions about the curriculum, assessment, and instruction. When supporting teachers in the use of formative assessment, it is crucial to take these psychological characteristics into account. Therefore, "much more attention needs to be paid to the psychological states of teachers and leaders, as what they do most likely is derived from what they think about what they do and who they serve." (Evans, 2009, p. 87).
The factors that influenced DBDM and AfL mostly overlapped, but there were also differences. For DBDM, the most evidence was found for data literacy, collaboration in the use of data, a positive attitude around the use of data, and goal setting. For AfL, feedback strategies, PCK, assessment literacy, and the facilitation of classroom discussions were the factors for which most evidence could be found in the literature. In their classroom practice, teachers are likely to integrate aspects of DBDM and AfL (Kippers et al., 2018), which suggests that all of the prerequisites discussed above matter. Further studies can use the framework developed in this review to examine the relative and joint importance of these prerequisites.

Limitations
Although this review provides a useful overview of critical teacher prerequisites for formative assessment in classroom practice, we must consider the limitations of this study. First, although this review identified various critical teacher prerequisites, we do not claim that this list of factors is exhaustive. It is possible that there are other critical prerequisites that have not yet been studied empirically. Second, it is possible that despite conducting an extensive literature search, some relevant literature was not retrieved. Further, by focusing only on peer-reviewed high-quality publications, we may have missed important information from other sources, for example, book chapters and conference proceedings. However, we choose this focus to ensure that our review only included publications that had undergone a rigorous peer review process. Moreover, a common problem with systematic reviews is that they often reflect a certain type of bias, such as author bias (e.g., the author decides what publications to include, without clear criteria) and publication bias (e.g., publications with positive effects have a higher chance of being published than publications with no effect) (Green et al., 2006). Some of these biases were avoided by employing detailed, rigorous and explicit methods, focused on a specific research question (Sackett, Straus, Richardson, Rosenberg, & Haynes, 2000). Furthermore, we developed clear inclusion criteria (Sackett et al., 2000) to overcome possible author biases in selecting literature. Moreover, we described the methodology used in a detailed manner (Green et al., 2006), and used a scoring system to determine the quality of each publication (Sackett et al., 2000). Finally, in the discussion section we linked our results to several well-known, albeit not always empirical, publications in the field (i.e., Beck & Nunnaley, 2020;Daly, 2010;Hamilton et al., 2009;Heritage, 2007;Mandinach & Gummer, 2011. Our review highlighted the importance of several factors beyond these existing models, most importantly, psychological factors. Because of the rigorous process we followed (Green et al., 2006), we believe that this review makes a valuable contribution to the field of formative assessment, one on which follow-up research can be based.

Implications for further research
This study provides an overview of the teacher factors enabling or hindering (which often results from the lack of enablers) the use of formative assessment in the classroom. A lot of evidence was found for some factors (e.g., data literacy, collaboration, attitude). However, this does not imply that these are the most important enablers. Less evidence was found for some factors, simply because these factors have not been investigated in many studies. Moreover, most of the studies had qualitative designs. Although these studies provide valuable insights into how certain factors influence teachers' use of formative assessment, they are not informative regarding the extent of the impact of these factors. Future large-scale quantitative studies can address this identified gap in the literature.
Furthermore, the results of this review show that different factors seem to influence the different approaches to formative assessment. For example, for AfL, we found that the use of feedback strategies and involving students influenced the use of AfL in the classroom. Although involving students and the use of feedback are likely to be important for DBDM, we found no studies that addressed these factors. Moreover, Table 2 shows that the majority of DBDM studies did not involve students. Involving students in DBDM research would be a critical first step to gain insights into how students can effectively be involved in DBDM implementation. Further research is needed on how to involve students in the process of formative assessment, and in DBDM specifically, as well as on the use of feedback by students. K. Schildkamp, et al. International Journal of Educational Research 103 (2020) 101602

Implications for practice
This review identified various teacher prerequisites needed for the use of formative assessment in classroom practice. There is some evidence that professional development can address (some of) these prerequisites (Schildkamp & Poortman, 2015;Schildkamp & Teddlie, 2008;Schildkamp & Visscher, 2010b;Staman et al., 2014). However, professional development does not always lead to the desired effects. More research is needed into the characteristics of effective professional development in the use of formative assessment, and into the development, implementation, and evaluation of professional development in the use of formative assessment. The evidence-based framework developed in this review can inform such research.
It is important to stress here that both DBDM and AfL are needed in schools, as these approaches can complement each other (Van der Kleij et al., 2015). The identified factors can support schools in the implementation of DBDM, or as Jimerson, Garry, Poortman, and Schildkamp (2020) stated, slow down data use. This refers to the process of collective in-depth data use, identifying challenging problems, positing hypotheses related to these problems, and collecting and interpreting data to inform changes in instructional practices. The identified factors also need to be taken into account when implementing AfL, which is faster-paced, and more focused on the use of in-the-moment assessment data by teachers and students to inform teaching and learning in everyday practice (Van der Kleij et al., 2015;Heritage, 2007).
In conclusion, this review focused on an underexposed aspect of formative assessment that is essential for its successful use in classroom practice: teacher prerequisites. This review was conducted in a comprehensive and systematic manner, and synthesized evidence from 54 studies. The results confirm the importance of the role of the teacher in the use of formative assessment, and identify a number of crucial influential factors that need to be taken into account. The prerequisites identified can inform professional development initiatives in schools with regard to DBDM and AfL, as well as teacher education programs. Only when proper support is planned for, and the factors that enable the use of formative assessment are in place, can formative assessment lead to the desired effects: improved student learning and achievement.