Assessment-based school accountability reforms have swept through the states, often including both new standardized tests for students and consequences for teachers, schools, and districts. Beginning with state level reforms that varied in strength and composition, school accountability has become more standardized with the passage at the national level of the No Child Left Behind Act of 2001 (NCLB). The expressed purpose of these reforms has been to promote educational achievement and reduce the disparity in educational opportunities between students. Encouragingly, several studies suggest that the state-level accountability reforms have increased student achievement (Carnoy and Loeb 2003, Hanushek and Raymond 2005). Similarly, the National Assessment of Educational Progress shows gains in mathematics and reading performance for 9 year olds and in mathematics performance for 13 year olds nationally during the past decade, perhaps as a result of standards and accountability.