Abstract International comparisons reveal large cross-country differentials in average student performance. Although there is considerable public debate about these differences, their sources are hardly identified. Using school, teacher and student data from the Third International Mathematics and Science Study (TIMSS), the present paper attempts to explain what causes between-country gaps in mathematics test score distributions. Following a three-pronged strategy of microlevel and cross-country regressions as well as bilateral country comparisons, we show how these gaps are explained by differences in school, teacher and student characteristics, or financial resources devoted to the school system. Institutional characteristics, such as competition between schools and the composition of the faculty can also help to understand international differences in student achievement.
