Charter schools show no significant overall impacts on achievement: Mathematica study

Issue: Charter schools are an important and growing component of the public school system in the United States. As of the 2009-2010 school year, more than 5,000 charter schools served over 1.5 million students—approximately three percent of all public school students—in 40 states and the District of Columbia. Charter schools are intended to play a key role in school improvement under the existing Elementary and Secondary Education Act (No Child Left Behind), as well as the programs established under the American Recovery and Reinvestment Act of 2009. However, there remains considerable debate as to whether, how, and under what circumstances charter schools improve the outcomes of students who attend them.

Study: Mathematica Policy Research recently completed a large-scale randomized trial of the effectiveness of charter schools, the most comprehensive charter school study of its kind to date to use an experimental design. The evaluation, funded by the U.S. Department of Education’s Institute of Education Sciences, covers 36 charter middle schools across 15 states and a sample size of 2,330 applicants. It compares outcomes of students who applied and were admitted to these schools through randomized admission lotteries (lottery winners) with the outcomes of students who also applied to these schools and participated in the lotteries but were not admitted (lottery losers). This experimental research design produces the most rigorous estimates of charter school impacts on student outcomes. The study’s results apply to this group of participating charter middle schools that held lotteries, and do not necessarily apply to the full set of charter schools in the U.S.


On average, charter middle schools that hold lotteries are neither more nor less successful than traditional public schools in improving student achievement in reading and math. However, these averages mask wide variation across individual charter schools in their impacts.

Study charter schools were more effective for lower income and lower achieving students and less effective for higher income and higher achieving students. In addition, charter schools in large urban areas had positive impacts on students’ achievement in math; those outside these large urban areas had negative impacts on achievement.

Study charter schools did not significantly affect most of the other outcomes examined, including attendance, student behavior, and survey-based measures of student effort in school.

These charter schools did positively affect levels of satisfaction with school among both students and their parents.

Quote: “This report helps us make sense of previous charter school studies that have generated a wide range of findings,” said Phil Gleason, senior fellow and lead author. “In this study—the most comprehensive and geographically diverse using charter school lotteries to date—our findings are consistent with prior evaluations that focused on a broad range of schools. We found that the average charter school in our sample did not have positive impacts on students’ math or reading achievement. And like previous lottery-based studies that have focused on single, urban districts, we found that charter schools in large urban areas and those serving a more disadvantaged student population had positive impacts on students' achievement in math."

Report: “The Evaluation of Charter School Impacts.” Philip Gleason, Melissa Clark, Christina Clark Tuttle, and Emily Dwoyer, June 2010. Executive Summary.

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