Revisiting The CREDO Charter School Analysis
Most people involved in education policy know exactly what you mean when you refer to “the CREDO study.” I can’t prove this, but suspect it may be the most frequently mentioned research report over the past two years (it was released in 2009).
For those who haven’t heard of it (or have forgotten), this report, done by the Center for Research on Education Outcomes (CREDO), which is based at Stanford University, was a comparison of charter schools and regular public schools in 15 states and the District of Columbia. Put simply, the researchers matched up real charter school students with fictional amalgamations of statistically similar students in the same area (the CREDO team called them “virtual twins”), and compared charter school students’ performance (in terms of test score gains) to that of their “twins.” The “take home” finding – the one that everybody talks about – was that, among the charter schools included in the analysis, 17 percent had students who did better on the whole than their public school twins, in 37 percent they did worse, and in 46 percent there was no statistical difference. Results varied a bit by student subgroup and over time.
There are good reasons why this analysis is mentioned so often. For one thing, it remains the largest study of charter school performance to date, and despite some criticism that the “matching” technique biased charter
