The public narrative surrounding efforts to improve low-performing K-12 schools in the United States has been notably gloomy. But what is known empirically about whether school improvement works, which policies are most effective, which contexts respond best to intervention, and how long it takes? We meta-analyze 141 estimates from 67 studies of…

High-stakes tests are the most heavily weighted measures in accountability systems developed in response to No Child Left Behind. While some studies show high-stakes accountability being related to test score gains, others suggest these policies do not improve achievement and often result in unintended consequences. To understand mechanisms…