Meta-Analysis Suggests Modest Impact of Charter Schools on Student Test Scores

A recent meta-analytic review indicates that the effects of charter schools on student test scores are generally small, with mathematics scores showing the most significant gains. According to a social media post by Crémieux, the largest estimated effect observed in the study was equivalent to approximately 1.35 IQ points for mathematics, which consistently demonstrated greater improvements than reading scores.

This finding aligns with broader research into charter school effectiveness, which frequently reports modest, yet often positive, impacts on student achievement. Other comprehensive meta-analyses, such as those by Betts and Tang, typically quantify these effects in terms of standard deviations or percentile gains. For instance, one such review found average math gains for charter school students to be around 0.084 standard deviations, translating to about a 3.3 percentile point increase in middle school math over one year. Reading gains are often less consistent or statistically significant in these broader analyses.

The interpretation of "small" effects varies among educational researchers. While a 1.35 IQ point gain might be considered modest, some studies, particularly those focusing on "No Excuses" charter schools, describe similar effect sizes (e.g., 0.25 standard deviations in math) as "large and meaningful" in the context of narrowing achievement gaps for disadvantaged students. These "No Excuses" models, characterized by high expectations and extended instructional time, tend to show stronger positive outcomes.

Overall, the research highlights a complex landscape of charter school performance. While benefits are often observed, especially in mathematics, the magnitude of these gains can be subject to different metrics and interpretations, and effectiveness can vary significantly based on school type, location, and student demographics.