The goals of NCLB (No Child Left Behind) are to improve the performance of American schools by mandating the standards of accountability for states, school districts and schools, as well as empowering parents by choosing better schools for their children to attend. NCLB Act required all American schools to meet AYF targets for proficiency, participation, and other academic indicators. Schools that do not meet AYP targets for two consecutive years or more are identified as ”in need of improvement” and must be subject to a series of sanctions. The sanctions contain that failing schools provide all students the option to transfer to highly performing schools, offer supplemental educational services, take corrective action, restructure school organization, or are taken over by school districts or states, for which the sanctions stiffen each subsequent year.The Bush's administration imposed the NCLB accountability systems on all schools and requested them to achieve provision of 100 percent of highly qualifies teachers by 2006 and close the achievement gap between the advantaged and the disadvantaged groups of students by 2014. Despite the widespread support for NCLB's goals, the growing state and local dissent and law suites against NCLB began to emerge as the public witnessed the law's negative effects on teaching and learning. In order to understand the controversies made by NCLB's interventions, this article looks for implications of the NCLB Act on educational reform in the U.S. Firstly, the paper overviews the initiating and implementing process of NCLB Act. Then the paper discusses key mechanisms and the major disputes resulted from the NCLB's accountability systems. Third, the paper interprets the constraint and possibility of the NCLB Act that has an attempt to integrate equity with accountability for educational policy and practice. And last, by introducing the Obama administration's proposal of revision of NCLB Act, the paper concludes that the current accountability system is in need of being much more comprehensive than the Bush administration thought it was.