- Jessalynn James
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Few topics in education policy have received more attention than teacher turnover—and rightly so. The cost of losing a good teacher can be substantial and is born most directly by students. It is now widely recognized that teachers differ considerably in their ability to improve student outcomes, but discussions of teacher turnover rarely reflect these differences. Instead, we typically treat teacher turnover as uniformly negative. In this paper, we examine teacher turnover in the context of rigorous teacher evaluation to explore three questions. How does teacher turnover affect the quality of teaching and student achievement? How does teacher turnover vary by measured teaching effectiveness? And to what extent is the turnover of effective teachers associated with the evaluation system? We examine these questions employing data from the District of Columbia Public Schools. We find that in general turnover improves teacher quality and student achievement, but that this result masks large differences between teachers identified as more and less effective. Turnover among more effective teachers is relatively low, and when more-effective teachers exit, they infrequently report the evaluation system as a reason.
Ten years ago, many policymakers viewed the reform of teacher evaluation as a highly promising mechanism to improve teacher effectiveness and student achievement. Recently, that enthusiasm has dimmed as the available evidence suggests the subsequent reforms had a mixed record of implementation and efficacy. Even in districts where there was evidence of efficacy, the early promise of teacher evaluation may not sustain as these systems mature and change. This study examines the evolving design of IMPACT, the teacher evaluation system in the District of Columbia Public Schools (DCPS). We describe the recent changes to IMPACT which include higher performance standards for lower-performing teachers and a reduced emphasis on value-added test scores. Descriptive evidence on the dynamics of teacher retention and performance under this redesigned system indicate that lower-performing teachers are particularly likely to either leave or improve. Corresponding causal evidence similarly indicates that imminent dismissal threats for persistently low-performing teachers increased both teacher attrition and the performance of returning teachers. These findings suggest teacher evaluation can provide a sustained mechanism for improving the quality of teaching.