The Mathematica Evaluation of Charter Middle Schools

The most rigorous study yet on the average impact of charter schools came out in June 2010. I remember that study, which just about everybody else in the world seems to have forgotten, because for the past two years it has been the thing I pointed to when I said that I wanted to start blogging.

I now find myself in the unfortunate position of writing my first blog post on this study, having found this morning that the press reception to it at the time was pretty much crickets. The most extensive article on the evaluation was a brief piece from CSM.

Anyway, the authors of the study emphasized that the average effect of the charter schools was zero, but with significant heterogeneity: charter schools that served poor kids in urban areas were far more likely to improve their test scores, while charter schools that served wealthy suburban kids tended to have negative effects on their test scores. The pretty clear interpretation of this is that charter schools serving poor kids are better than charter schools serving rich kids.

The point I've been wanting to make for the last two years (aren't you just waiting with baited breath?) is that the study doesn't show that at all. Your faithful correspondent was one of the half-dozen people lucky enough to be sitting in a webinar in July 2010 to find that out.