UPDATE: This fantastic Gotham Schools article explains that New York's rating system was designed to guarantee that "effective" and "ineffective" teachers would be found all over the city. Which renders the New York Times story--and my post--basically moot.
Still, this wasn't the first bit of evidence showing that we might not have a teacher effectiveness gap, or at least much of one. This rigorous CALDER study, in particular, found that:
The average effectiveness of teachers in high-poverty schools is in general less than teachers in other schools, but only slightly, and not in all comparisons. The authors also find differences in within-school-type variation in teacher effectiveness in nearly every comparison. These differences are largely driven by the longer tail at the bottom of the teacher effectiveness distribution in high-poverty schools. Teachers at the top of the effectiveness distribution are very similar across school settings.
So the evidence on the lack of a gap isn't as open and shut as my post implies. But it certainly appears likely that the gap is much smaller than we once thought -- which does call for pushing the pause button on massive efforts to move teachers around.
The finding -- reported by the Times this weekend -- that really good, and really bad, teachers are evenly distributed around New York City is jaw-dropping news. It upends everything we thought we knew about teacher quality, especially the notion that our achievement gap is caused in large part by a "teacher quality gap," with the worst teachers clustered in the neediest schools. But they aren't. So now what?
Let me stipulate that this finding might be incorrect (though previous analyses have come to similar conclusions). Maybe it's harder for teachers in affluent schools to show strong value-added gains, because their students are already topping out on the tests. Perhaps student mobility is making teachers in high-poverty schools look better than they really are. (Their worst students don't show up for testing -- or have already moved onto another school.)
But assume it's true. What are the implications?
We have a lot of problems in K-12 education to address. Let's be grateful that we can take "closing the teacher effectiveness gap" off our to-do list.
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