NEPC Review: A Meta-Analysis of the Literature on the Effect of Charter Schools on Student Achievement (Center on Reinventing Public Education, August 2014)
This report attempts to examine whether charter schools have a positive effect on student achievement. From a review of 52 studies that the authors considered superior (40 of them used in an earlier report),it finds charters are serving students well, particularly in math. This conclusion is overstated; the actual results are not positive in reading and are not significant in high school math; for elementary and middle school math, effect sizes are very small, ranging from 0.03 to 0.08 s.d. The report does a solid job describing the methodological limitations of the studies reviewed, then seemingly forgets those limits in the analysis. For example, the authors include lottery-based studies, considering them akin to random assignment, but lotteries only exist in charter schools that are much more popular than the comparison public schools from which students are drawn. This limits the study’s usefulness in broad comparisons of all charters versus public schools. The report also seeks to examine whether the effects of charter schools have changed over time. Despite finding no change, the authors inexplicably assert that there is a positive trend. Claims of positive effects when they are not statistically significant, exaggeration of the magnitude of effects, reliance on simple vote-counts from a selected sample of studies, and unwarranted extrapolation of the available evidence to assert the effectiveness of charter schools further render the report of little value for informing policy and practice.