Annual student testing may make it possible to measure the contributions to student achievement made by individual teachers. But would these “teacher value-added” measures help to improve student achievement? I consider the statistical validity, purposes, and costs of teacher value-added...

Given scarce resources for evaluation, we recommend that education researchers more frequently conduct comprehensive randomized trials that generate evidence on how, why, and under what conditions interventions succeed or fail in producing effects. Recent experience evaluating a randomized...