In the United States, policies in forty states and D.C. incorporate student growth measures--estimates of student progress attributed to educators--into educator evaluation. The federal government positions such policies as levers for ensuring that more students are taught by effective teachers and that effective educators are more equitably…

Effective teaching has long been an issue of national concern, but in recent years focus on the effectiveness of programs to produce high-quality teachers has sharpened. Long-standing achievement gaps persist despite large-scale legislative changes at the federal and state levels, and American students continue to show poorer performance on…