This study examines the variation in educational outcomes across and within countries using the TIMSS mathematics tests. It documents the wide cross-country variation in the level and dispersion of test scores. Countries with the highest test scores are those with the least inequality in scores, which suggests a “virtuous” equity-efficiency trade-off in improving educational outcomes. Analyzing the association of gender, immigrant status, and family background factors with scores, we find large cross-country differences in the relation between those factors and scores.