It's not the science that is junk, it's the measures, Part II
So a day or so after my last post, It's not the science that is junk, it's the measures, I came across this interview of Jesse Rothstein by Rachel Cohen in the American Prospect. There's lots of good stuff in there and it's worth reading. I don't mean to take away from the import of Jesse Rothstein's work (I am a big fan of his work and of Rachel Cohen's work) but a piece of it kind of demonstrates what I was trying to get at in my last post.
Talking about VAM, Rothstein said,
It’s very controversial and I’ve argued that one of the flaws of it is that even though VAM shows the average growth of a teacher’s student, that’s not the same thing as showing a teacher’s effect, because teachers teach very different groups of students.
If I’m a teacher who is known to be really good with students with attention-deficit disorder, and all those kids get put in my class, they don’t, on average, gain as much as other students, and I look less effective. But that might be because I was systematically given the kids who wouldn’t gain very much.So, yes, this is a very good point: there is a difference between showing "the growth of a teacher's student" and "showing a teacher's effect." And yes, according to test scores, and how well students perform on them, teachers can look more effective or less effective, regardless of how good they are at teaching.
The he says, when she asks if he is skeptical of VAM,
I think the metrics are not as good as the plaintiffs made them out to be. There are bias issues, among others. One big issue is that evaluating teachers based on value-added encourages teachers to teach to the state test.
During the Vergara trials you testified against some of Harvard economist Raj Chetty's VAM research, and the two of you have been going back and forth ever All Things Education: It's not the science that is junk, it's the measures, Part II: