Charter Schools: Are They Effective?

Prepared for
U.S. Department of Education

Designed to free educators from bureaucratic regulations and encourage innovations, charter schools are public schools that have been granted autonomy over their operations. They operate under a contract, or charter, with their state that specifies the conditions under which a school can operate and holds the school accountable for meeting certain terms, such as improving student performance. Since their inception in 1992, charter schools have played an important part in education reform. Today, there are more than 6,000 charter schools across 42 states and the District of Columbia.

At the same time, some have questioned whether charter schools promote student learning adequately, while others have raised concerns that charter schools admit only the most motivated students and may exacerbate racial segregation in public schools. Some critics have called for greater oversight of charter schools.

Mathematica conducted a national evaluation of charter schools, funded by the U.S. Department of Education, to address three key research questions:

  • What are the impacts of charter schools on students' achievement, students' school success, and parents' satisfaction?
  • In what ways are charter schools and conventional public schools different? What role do these differences play in determining student outcomes?
  • To what extent does the autonomy or policy environment under which charter schools operate influence their effectiveness?

The evaluation was based on an experimental design in which applicants were assigned by lottery to groups that were either admitted or not admitted to the schools. The evaluation included the following components:

  • Selection and recruitment of 36 charter middle schools from 15 states covering a broad geographic area and with laws that varied in the degree of autonomy offered to charter schools.
  • Random assignment of charter school applications through lotteries for admission at participating schools. Participating charter schools conducted lotteries as part of their admissions process, and these lotteries separate applicants into two groups: (1) applicants who were offered admission to the school by lottery, and (2) lottery participants who were not offered admission. We estimated the impacts of charter schools by tracking these two groups and comparing their outcomes over a two-year follow-up period.
  • Data collection on sample members over a baseline year and a two-year follow-up period. Quantitative data collection included administrative school records data on students' attendance, performance on standardized tests, and other outcomes; telephone surveys of students and their parents; and a mail survey of school principals.


We found that:

  • On average, charter schools had no significant impacts on student achievement in math and reading.
  • Impacts on measures of both student and parent satisfaction were positive and statistically significant.
  • Charter school impacts varied widely across schools.
  • Impacts were most positive among schools in large, urban areas and among those serving the most disadvantaged students.
  • Among subgroups of students, impacts were most negative among students who were not eligible for free or reduced-price school meals and those who were higher achieving when they entered charter schools.

Do These Schools Improve Students’ College Outcomes?

A follow-up study released in 2019 found that attending a charter middle school participating in the study did not affect students’ likelihood of enrolling in or completing college. Furthermore, a given school’s success in improving students’ achievement was not related to its success in improving their college enrollment and completion.