Jay Greene writes about the unions declaring war on charter schools (h/t Assigned Reading), but in the midst of his piece is some interesting data. One of the big (usually union) arguments against charter school performance is that those who apply are highly-motivated, self-selected students (or parents) and that, of course, they perform better. Greene cites three studies that took on that oft-heard talking point head-on:

The highest quality studies have consistently shown that students learn more in charter schools. In New York City, Stanford economist Caroline Hoxby found that students accepted by lottery to charter schools were significantly outpacing the academic progress of their peers who lost the lottery and were forced to return to district schools.

Florida State economist Tim Sass and colleagues found that middle-school students at charters in Florida and Chicago who continued into charter high schools were significantly more likely to graduate and go on to college than their peers who returned to district high schools because charter high schools were not available.
The most telling study is by Harvard economist Tom Kane (PDF) about charter schools in Boston. It found that students accepted by lottery at independently operated charter schools significantly outperformed students who lost the lottery and returned to district schools. But students accepted by lottery at charters run by the school district with unionized teachers experienced no benefit. {Links added – ed.}

The last point is interesting and bolsters the argument that it is the flexibility available to charter schools that plays a big part in successful outcomes. But charter schools are only a limited solution. Where their real value lies is in what they teach us about teaching kids. As Kane says:

The fact that there are large differences in subsequent performance suggests that the charter schools were indeed having an impact. The next step is to identify what’s working in charter schools that can be transferred back into the traditional public schools to improve student achievement.

Exactly. It will take a flexible education system to do that successfully.