Assessing Student Performance in Charter Schools

Why Studies Often Clash and Answers Remain Elusive

By Paul T. Hill

In recent months, researchers have rushed into print studies claiming to assess charter school effectiveness. The net effect of this barrage of findings is that we know little more than we did before. Results depend heavily on the schools studied and the methods used.

Everyone wants to know whether students in charter schools are learning more or less than they would have learned in conventional public schools. This is a reasonable question, but it is easier to ask than to answer. The answer is complicated for two reasons.

First, it is impossible to observe the same students simultaneously in both charter schools and the schools they would have attended if charter schools had not been available. Thus, it is necessary to create a “counterfactual” by comparing students in charter schools with other students who are similar in some ways but do not attend charter schools. Making appropriate comparisons is not so easy,...