Achievement Data Show Positive Impact of Charter Schools, Study Finds

Published February 1, 2005

Parents, teachers, and other school reformers who want to make full use of public charter schools to help students who are struggling in regular public schools received reinforcement from a new national study by Harvard University education researcher Caroline Hoxby. The study found that, nationwide, students in established charter schools score significantly higher on state reading and mathematics examinations than do their peers in conventional public schools.

The study, “Achievement in Charter Schools and Regular Public Schools in the United States: Understanding the Differences,” published in December 2004, is the most comprehensive look yet at the effect of charter schools on student achievement. It examines data for 99 percent of all elementary-level pupils in charter schools across the nation.

Charter schools are publicly funded schools that receive leeway to innovate in such areas as curriculum, management, and use of technology in exchange for a contractual pledge to deliver tangible results.

Previous Study Flawed

The New York Times gave front-page coverage last summer to a study by the American Federation of Teachers (AFT) that relied on data from a mere 3 percent sample of charter-school fourth-graders. The more comprehensive Hoxby study attracted no equivalent attention from the newspaper. Because charter schools enroll only 1.5 percent of all K-12 students, it is statistically important to include almost all of them in any valid study, Hoxby noted.

The AFT, whose leadership opposes the very existence of charter schools, claimed its data showed charter students scored lower than their peers in regular public schools. Their report failed to take into account the fact that charter schools serve a much higher proportion of children from low-income and minority homes than do public schools in general.

The Harvard study matches each charter school to the closest neighborhood public school, or the one with the most similar racial composition if there are more than one. Elementary pupils typically travel the shortest distance possible to school.

Among Hoxby’s findings:

  • Compared to students in the matched regular public school, charter students overall are 5.2 percent more likely to be proficient in reading and 3.2 percent more likely to be proficient in math.
  • Students in charters that have been in operation longer are more likely to have an advantage over their peers in conventional public schools. In reading, the edge is 2.5 percent for a charter school that has been up and running 1 to 4 years, 5.2 percent for a charter operating 5 to 8 years, and 10.1 percent for a charter school operating 9 to 11 years. Hoxby observed it is common for charter schools to improve substantially each year they are in operation. She also noted low-performing charter schools often fail to attract many students and usually exit the marketplace quickly.
  • While charters tend to spring up in areas where many students are disadvantaged and families have limited ability to exit troubled schools, charters with a high proportion of poor or Hispanic students show an extra advantage in their students’ test scores.

Other Aspects Important Too

While Hoxby’s findings present strong evidence of positive academic results, charter schools have demonstrated other advantages as well. In his new book, Creating the Capacity for Change, Minnesota school reformer Ted Kolderie explains the need for taking a broad perspective in measuring the success of innovative schools.

“New and different schools will require new kinds of assessment,” Kolderie argues. “It will be important to look with fresh eyes for what is working well in these schools. It may not be high scores. It may be gain on scores. Or it may be better attitudes, better attendance, more student initiative, greater curiosity about learning. Academics are important but not all-important. Safety is important. A healthy school culture is important. Empowerment is important. The public wants many things from its schools.”

Don Soifer ([email protected]) is executive vice president and Robert Holland ([email protected]) is a senior fellow at the Lexington Institute, a think tank in Arlington, Virginia. This article was first issued as a Lexington Institute Issue Brief on December 20, 2004 (

For more information …

The AFT charter school study is described in a November 2004 School Reform News article by Bob Holland, “Charter School Studies: Apples to Apples vs. Apples to Oranges,” online at

Caroline M. Hoxby’s December 2004 Report from Harvard University and the National Bureau of Economic Research, “Achievement in Charter Schools and Regular Public Schools in the United States: Understanding the Differences,” is available online at