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Years of test-score data suggest charter schools don’t harm traditional public schools

School choice opponents argue that school choice, such as charter schools, harm traditional public schools. Any gains made by students in charter schools, they say, comes at the expense of students left behind.

But according to Marcus Winters with the Manhattan Institute, years of test-score data suggest they don’t.

Using school-level test-score data across the United States made available by Stanford Education Data Archive (SEDA), I show that there is a very small but positive relationship between the proportion of students within a geographic district who attend a charter school as of 2009 and the test-score growth for students enrolled in the traditional public schools in the same district over the next seven years.

The analysis in this report is intended not to show causality, but rather to show that the general pattern of test-score outcomes over this period is simply not consistent with the claim that charter school exposure for a meaningful period of time produces declines in the performance of traditional public schools.

Winters’ analysis focuses on several years of math and English Language Arts test score growth of students enrolled in a traditional public school and the proportion of students enrolled in charter schools. He notes that charter school attendance as of 2009 had a positive, albeit small, effect on the test-score growth of students in traditional public schools in the same district over the next seven years.

Does this analysis rule out other factors that could have influenced test-score outcomes outside of charter school exposure? No. Does it offer a compelling counter to the argument that charter schools set back public schools? Yes. To those who would still argue that charter schools hurt students in traditional schools, Winters concludes that the “burden of proof” remains on them.