Private vs. Public Schooling: The role of school composition

Publicly funded private schooling is a common feature of many education systems, yet its implications for educational equity and effectiveness remain contested. While private schools often exhibit higher student achievement, the sources of this advantage are not well understood. In particular, differences in student composition—especially in terms of socioeconomic status (SES)—are likely to play a key role. This paper examines how school-level SES composition contributes to achievement differences between public and private schools. Using propensity score matching (PSM) on data from 22,441 French ninth-grade students, we find that private school students outperform their public school peers in mathematics and French, with especially large effects for low-SES students, an underrepresented group in private schools. While school composition explains only part of these effects, it accounts for a substantial share of the performance gap among high-SES students, rendering the adjusted effect statistically indistinguishable from zero. These findings highlight which students benefit most from private schooling and point to the need for further research into the mechanisms underlying performance differences across school sectors. • Private school students score higher than public peers in mathematics and French. • The achievement gap is largest among students from low socioeconomic backgrounds. • School composition fully explains the private school advantage among high-SES students. • For low-SES students, private schooling has positive effects beyond peer composition. • Findings highlight equity challenges in access to publicly funded private schools.