For more than two decades, federal law has required states to identify schools failing to provide students with a high-quality education and has led to substantial debate about how best to do so. Appropriately identifying the lowest performing schools matters because it allows state and local education agencies to target limited resources for school improvement to where they are needed most. The Every Student Succeeds Act (ESSA) of 2015 sought to address perceived problems with school accountability systems under prior federal law. ESSA provided states with increased flexibility in how they design their "annual evaluation of school performance." It also introduced new requirements for states' subsequent "identification of schools for the most intensive support," now designated as those needing Comprehensive Support and Improvement (CSI), in part to allow states to focus on a smaller set of the lowest performing schools. This report examines if ESSA played out as policymakers expected or if there were any other, perhaps less expected, consequences for the number, types, and composition of schools that states identified. The report examines this issue by comparing schools identified for the most intensive supports just before and just after ESSA's implementation.