There has been no shortage of newsmaking charter school studies over the last year. The biggest of the bunch was a national study of charter schools by Margaret Raymond and her colleagues at the Center for Research on Education Outcomes at Stanford University. It compared learning gains over the course of a school year for charter school students in 16 states to those of demographically similar students in nearby traditional schools. The bottom line: Although there was huge variation among the charter schools studied, the traditional school students, on the whole, appeared to learn slightly more than their charter school counterparts.
The study came in for some heavy criticism, though, in October from Caroline Hoxby, another Stanford researcher, after she conducted her own study of charter schools in New York City and reached the opposite conclusion. She said the CREDO study suffered from "a serious mathematical mistake" that may have biased the results in a downward direction.
Now the federal What Works Clearinghouse has waded into the debate. In its latest "quick review," the research agency concludes that the CREDO study was "consistent with WWC standards with reservations." It also adds a word of caution, though:
"Although the study matched charter school students to traditional public school students based on demographic characteristics and test scores, it is possible that there were other differences between the two groups that were not accounted for in the analysis, and these differences could have influenced achievement growth."
The CREDO researchers would probably not disagree. The question now is: Will we see a similar review from the clearinghouse of the New York City study? I'll be watching.