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How Charters Perform

Although there are as many as 200 studies of charter school effectiveness, only a handful use high-quality research methodologies.  Among those, a number show promise:

Year Research Organization Title Findings
2004 Caroline M. Hoxby, Harvard University and National Bureau of Economic Research Achievement in Charter Schools and Regular Public Schools in the United States: Understanding the Differences This study reviewed the performance of nearly every charter elementary school student in the country and compared their achievement against their counterparts at nearby district public schools. The study found charter students were more likely to be proficient in both reading and math than traditional public school students. Further, the study showed this trend to be even more prevalent in older charter schools. Students who attended charter schools that had been in operation for more than nine years showed the largest gains.
2009 Harvard Graduate School of Education and the Massachusetts Institute of Technology Informing the Debate: Comparing Boston's Charter, Pilot and Traditional Schools Charter school students in Boston outperform their peers at other public schools in Boston. The positive effects of charter schools on student achievement were found at both the middle and high school levels, and across subjects. The impact on middle school math was particularly dramatic - enough to move a student from the 50th to the 69th percentile in student performance in one year. At the high school level, charter students showed stronger performance scores in English language arts, math, writing topic development and writing competition. The charter school students in this study won school admission lotteries. To show that charters were not “creaming” the best achievers, students were compared against their counterparts who applied but did not win the lottery to attend a charter school.
2009 National Bureau of Economic Research and Stanford University How New York City’s Charter Schools Affect Achievement Under-served students who attended charter schools in New York City for nine consecutive years, from kindergarten to eighth grade, would close most of the “Scarsdale-Harlem” achievement gap. The charter school students in this study won school admission lotteries. To show that charters were not “creaming” the best achievers, students were compared against their counterparts who applied but did not win the lottery to attend a charter school.
2009 RAND Corporation Are Charter Schools Making a Difference? This study found that students attending charter high schools in Chicago and Florida had higher ACT scores, graduation rates and college entrance rates than their peers in traditional public schools.
2010 Mathematica Policy Research The Evaluation of Charter School Impacts This study looked at 36 charter middle schools in 15 states and found that overall, the charter students perform as well as those who returned to district schools after losing out in a lottery. However, these averages mask wide variation across individual charter schools in their impacts. 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.

    In addition, "Value-Added and Experimental Studies of the Effect of Charter Schools on Student Achievement," is the only report to date that tried to make sense of the findings across a variety of studies that used good research methods. The report found that charter schools produce positive effects in elementary and middle schools that far outpace other interventions such as class-size reduction.

    In conclusion, there is a great need for more longitudinal research on charter schools. The studies to date, even when favorable, often focus on a certain subset of the population, and do not produce outcomes that can necessarily be extrapolated to the entire sector.  However, they point to several factors – such as strong public policies and authorizing entities – that make a big difference in supporting high-quality public charter schools.