What to Think About the DC IMPACT Study

October 17, 2013

By Anne Hyslop

Few teacher evaluation reforms have been as contentious as the IMPACT system in D.C. Public Schools. But a new study published by Thomas Dee and James Wyckoff provides the first empirical evidence that the controversial policy could be encouraging effective teachers to stay in the classroom – and improve their practice.

Dee and Wyckoff examined teachers that scored on the cusp of various IMPACT performance levels– namely, teachers just above and just below the cutoff for effective and highly effective (HE) ratings. The idea is that teachers near the cut points share similar characteristics, regardless of their final rating. By examining these teachers’ outcomes in subsequent years, researchers can isolate the effect of IMPACT’s incentives on teacher behavior. Do teachers that barely receive a HE rating fare differently than those that just missed the distinction? And do minimally effective (ME) teachers close to the effective cut point respond differently than teachers who barely cleared the effective hurdle?

Turns out, they do. The incentive structure within IMPACT had significant effects on retention and performance, particularly after the second year of implementation (2010-11) when IMPACT gained credibility. At that time, teachers with two ME ratings became eligible for termination and those with two HE ratings earned permanent salary increases, not just bonuses. Teachers that received their first ME rating after the 2010-11 year were significantly more likely to leave DCPS (over 10 percentage points) than teachers that scored just above the cut point. Further, the threat of dismissal improved the performance of ME teachers that chose to stay for the 2011-12 year – their scores improved by 12.6 IMPACT points compared to teachers that just received an effective rating, an increase of five percentile points. Similar effects were seen for teachers that could become eligible for increases in their base pay if they remained HE – their 2011-12 IMPACT scores improved by nearly 11 points compared to teachers that missed the HE cutoff, an increase of seven percentile points.

So what do these results tell us about IMPACT and teacher evaluation reform overall? Is this a moment for cautious – or all-out – optimism?