A new study that examines test scores from 29 countries concludes that competition from private schools improves achievement for students in both public and private schools.
Martin R. West, an assistant education professor at Brown University, and Ludger Woessmann, an economics professor at the University of Munich in Germany, find that a 10 percent increase in the share of national student enrollment at private schools leads to an average improvement that is nearly equal to half of a year’s worth of learning in mathematics, and a gain that is equivalent to more than one-fifth of a grade level in science and reading.
The researchers used standardized test data from the Organization for Economic Cooperation and Development’s Program for International Student Assessment, or PISA. An overview of the research appears in the winter edition of Education Next, published by the Hoover Institution at Stanford University.
The researchers say differences in the extent of private schooling in the nations studied stems largely from the Catholic Church’s 19th-century construction of its own schools in certain countries.
The study sought to “capture only that share of the private sector’s size that can be attributed to 19th-century Catholic policies,” and use that estimate “to isolate the causal effect of private school competition on the achievement of individual students across 29 countries.”
The researchers say they also sought to adjust for many other factors, such as family background and other national characteristics beyond the role of Catholic schooling.
A version of this article appeared in the October 22, 2008 edition of Education Week