Educational inequality across countries: An integrative data analysis of TIMSS 2023 data

Socioeconomic disparities in educational achievement remain a central challenge for education systems. This study examines cross-national variation in the relation between socioeconomic status (SES) and Grade 8 mathematics achievement, using data from TIMSS 2023. Employing an integrative data analysis approach, we estimated within-school, between-school, and contextual SES effects for 43 countries and applied random-effects meta-regression to examine system-level moderators. Results show that SES is a consistent predictor of achievement within schools, while between-school SES effects were substantially larger, indicating pronounced compositional inequalities. The pooled contextual SES effect was large (ES2 = 0.85, 95% CI [0.74, 0.95]) and highly heterogeneous across countries (τ² = 0.11; Q(42) = 642.40, p < .001), ranging from negligible in Nordic systems to very large in more stratified systems. Random-effects meta-regression analyses revealed that income inequality and between-school segregation strongly predicted contextual SES effects, whereas higher levels of democratic governance were associated with weaker effects.