Study Measures Impact of Private Schools

Countries with a higher private school enrollment rate perform better on math, science, and reading exams, but also have lower overall education expenditures, according to a study published in August by Harvard Graduate School of Education professor Martin R. West and University of Munich economics professor Ludger Woessmann.

A survey across 29 nations suggests that competition to the public school system provided by private schools enhances productivity in K-12 education, West said—in contrast to an alternative argument that the existence of private schools increases inequality in education.

Analyzing test data of 220,000 students from the Programme for International Student Assessment, West and Woessmann showed that a 10 percent increase in enrollment in private schools results in an improvement in math test scores equivalent to almost a half year’s worth of learning and a reduction in per-student education spending by over 5 percent of the average for Organization for Economic Co-operation and Development countries.

The presence of a strong private sector also improved the achievement of students who attended public schools, even though high-ability students may tend to self-select into private schools, the study found.

According to West and Woessmann, theirs was the first study to attempt to measure the causal impact of competition by looking at variation in competition among different countries.


The study established a causal relationship between private school enrollment and performance of the education system by examining the Catholic church’s efforts in the 19th century to establish Catholic schools in various non-Catholic countries.

This allowed West and Woessmann to isolate the effect of education system competition from private schools on students’ performance today.

“The amount of competition in education today varies from one country to another for reasons that have little to do with contemporary school quality, or national income, or commitments to education,” the researchers wrote in the study, instead pointing to the role of the Catholic church.