Probably the most commonly cited national study on charter school performance is a 2013 study by the Center for Research on Education Outcomes (CREDO) at Stanford. It analyzed charter results between 2008 and 2011 in 27 states, covering over 95% of the students in charter schools. The report found small benefits to attending a charter school in terms of reading achievement and no noticeable difference in math achievement.
A 2014 meta-analysis that included 52 high-quality studies published from 2001 to 2013 of charter school performance found that charter schools, on average, had positive impacts on students’ math achievement relative to traditional public schools in most grade groupings. No statistically significant differences were found in reading.
Julian R. Betts and Y. Emily Tang: A Meta-Analysis of the Literature on the Effect of Charter Schools on Student Achievement, August 2014.
Center for Research on Education Outcomes: National Charter School Study: Executive Summary, 2013