Study Finds D.C.'s Controversial Teacher- Evaluation System Is Working. The IMPACT system—started by Michelle Rhee when she was chancellor of Washington's public schools— has caused more low-performing teachers to leave the school system and seems to have improved the performance of both strong and weak teachers, according to a study by Thomas Dee of Stanford University's Graduate School of Education and James Wyckoff of the Curry School of Education at the University of Virginia. Teachers judged effective, by classroom observation and test scores, received significant raises. The New York Times's Economix blog has a good review of the findings released last week, while the American Enterprise Institute's Rick Hess in Education Week offers some thoughts on what makes IMPACT unique.
Teachers in the United States are compensated largely on the basis of fixed schedules that reward experience and credentials. However, there is a growing interest in whether performance-based incentives based on rigorous teacher evaluations can improve teacher retention and performance. The evidence available to date has been mixed at best. This study presents novel evidence on this topic based on IMPACT, the controversial teacher-evaluation system introduced in the District of Columbia Public Schools by then-Chancellor Michelle Rhee. IMPACT implemented uniquely high-powered incentives linked to multiple measures of teacher performance (i.e., several structured observational measures as well as test performance). We present regression-discontinuity (RD) estimates that compare the retention and performance outcomes among low-performing teachers whose ratings placed them near the threshold that implied a strong dismissal threat. We also compare outcomes among high-performing teachers whose rating placed them near a threshold that implied an unusually large financial incentive. Our RD results indicate that dismissal threats increased the voluntary attrition of low-performing teachers by 11 percentage points (i.e., more than 50 percent) and improved the performance of teachers who remained by 0.27 of a teacher-level standard deviation. We also find evidence that financial incentives further improved the performance of high-performing teachers (effect size = 0.24).