A growing body of research recognizes the critical role of the school principal, demonstrating that school principals' effects on student outcomes are second only to those of teachers. Yet policy makers have often paid little attention to principals, choosing instead to focus policy reform on teachers. In the last decade, this pattern has shifted…

In 2011, the U.S. Department of Education granted states the opportunity to apply for waivers from the core requirements of the No Child Left Behind Act. In exchange, many states implemented systems of differentiated accountability that included a focus on schools with the largest achievement gaps between subgroups of students. We use…