The Evaluation of Charter School Impacts

Charter schools, first launched in the 1990s, are an important and growing component of the public school system in the United States. As of November 2009, 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 (Center for Education Reform 2009). 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. This report summarizes the results of a new study: the Evaluation of Charter School Impacts, a large-scale randomized trial of the effectiveness of charter schools funded by the Institute of Education Sciences and conducted by Mathematica Policy Research and its partners.1
The evaluation, which we conducted in 36 charter middle schools across 15 states, compares outcomes of students who applied and were admitted to these schools through randomized admissions 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 analytic approach produces the most reliable impact estimates. But because the study could only include charter middle schools that held lotteries, the results do not necessarily apply to the full set of charter middle schools in the U.S.