Interpreting the Important New Research on D.C.'s IMPACT System

October 18, 2013

By Frederick M. Hess

So, it turns out that Michelle Rhee knew what she was doing. Stanford’s Tom Dee and the University of Virginia’s Jim Wyckoff have just published an important study on Washington D.C.’s controversial teacher-evaluation system. They find that the IMPACT system launched by former chancellor Michelle Rhee appears to boost teacher effectiveness and also makes it more likely that low-performing teachers will depart. Deservedly, he study got a lot of attention yesterday, including in the New York Times and the Washington Post.

Making clever use of regression-discontinuity design, the authors note that IMPACT appears to aid students both by “avoiding the career-long retention of the lowest-performing teachers and through broad increases in teacher performance.”

This is good news for advocates of more sensible teacher evaluation and pay. That said, there’s also the risk that reformers will misinterpret the findings or fail to understand why the D.C. IMPACT system seems to have delivered where seemingly similar efforts have previously disappointed. Before pointing to Dee-Wyckoff as proof that aggressive teacher evaluation “works,” would-be imitators need to take a good look at what the D.C. public schools have actually done. Three key ones deserve note, especially for policymakers.