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.