The Center for Research on Education Outcomes (CREDO) at Stanford University conducted an analysis of the differences in student performance at charter schools and traditional public schools in the state of Michigan. In contrast to the majority of prior evidence regarding charter effects in the U.S., which tends to show no impact, the study finds an overall small positive effect of being in a charter school. As with CREDO’s previous reports on charter schools, the study employs a large and comprehensive dataset and fairly solid analytic methods, making this study a contribution to the literature on charter school effectiveness. However, there are significant reasons for caution in interpreting the study’s results. In particular, the plausibility of any causal inferences depends on the premise that the seven matching variables are sufficient to account for all meaningful differences between students in charter and traditional public schools. Additionally, important details of the analytic methods are missing from the report, making it unclear whether the researchers have addressed previously identified issues with their approach concerning, e.g., the stability of the student population used as a comparison group. Finally, even setting aside issues with the study’s methods, the actual magnitudes of the effects reported are extremely small.
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