Recent studies on value added research indicates that, by using data from student perceptions, classroom observations, and test score growth, one can obtain credible evidence of the relative effectiveness of a set of teachers who teach similar children under similar conditions. Recent careful research on school effects indicates that committed educators working collectively can create a learning environment in which low-income minority youth thrive academically. Taken together, these two lines of research inspire optimism about educational improvement.The two strands of research, however, are insufficient guides for action. To act, more informative evidence and a theory to synthesize all of the evidence are needed. Research on value added has no implications for action in isolation from other research about effective schooling because, like any research program, the narrow conditions that make value-added research convincing limit its direct applicability in practice. However, in combination with a wide range of related research and a coherent theory of action, research on teacher effectiveness indicators can increase the potential for educational improvement.