The conventional wisdom in Washington education policy circles these days is that reforms to teacher evaluation haven’t worked. The new Every Student Succeeds Act cancels Obama administration incentives for states to pursue evaluation reform and blocks the U.S. Department of Education from mandating future action.
The targeting of the lowest-performing teachers for dismissal—something that rarely happened in public education prior to the introduction of new, more rigorous evaluation systems in many states in recent years—has been especially controversial.
But new research on one of the most contentious new-generation evaluation systems, the District of Columbia’s IMPACT model, now in its seventh year, has found that the departure of low-rated teachers under the system, combined with a push to recruit strong replacements, has led to higher student achievement in schools in Washington’s most disadvantaged neighborhoods.
Researchers Tom Dee of Stanford, Jim Wyckoff of the University of Virginia and colleagues compared the combined IMPACT scores and the student achievement of teachers who departed Washington’s public schools in 2010, 2011, and 2012 with the performance of replacement teachers the following year and found that IMPACT “targets the exit of low-performing teachers” and that doing so “substantially improves teaching quality and student achievement in high-poverty schools.”
The D.C. school system uses multiple evaluations by multiple evaluators (including experts from outside teachers’ schools), student test scores and other factors to rate teachers. Dee and Wyckoff found that the annual attrition level of the city’s low-performing teachers—those rated “ineffective” or “minimally effective”—was 46 percent, more than three times the attrition rate among high-performing teachers.
They found that students with replacement teachers learned the equivalent of between a third and two-thirds of a year of additional study in math, and nearly as much in reading. More than 90 percent of the turnover of low-performing teachers occurred in Washington’s high-poverty schools, Dee and Wyckoff reported.
At the other end of the performance spectrum, highly-rated teachers who left the school district voluntarily were replaced on average by somewhat less effective teachers. But the departure of the higher-performing teachers had less impact on the district’s results than the departure of low-achievers.
The key to Washington’s trading-up strategy, the researchers note, is the city’s ability to sustain a supply of strong replacement teachers.
D.C. school officials have poured new resources into teacher recruitment in the face of tough competition for top teachers from a charter sector that educates nearly half the city’s public school students. And they’ve been helped by the fact that Washington is a magnet for talented millennials.