Education is one of the most commonly proposed determinants of social trust (generalized trust). Nevertheless, the empirical evidence of a causal relationship between education and social trust is inconclusive. This study contributes to this discussion in two ways. First, its design provides strong grounds for causal inference across multiple countries by exploiting numerous European compulsory schooling reforms. Second, it considers how the structure of education, specifically between-school tracking, impacts the relationship between education and social trust. The article argues that less tracking is positive for social trust because it entails intergroup contacts between children with different social backgrounds. The results do not give support for a general positive effect of education on social trust as the effect of reforms that extend compulsory education is positive but small and not statistically significant. However, reforms that reduce tracking have a somewhat larger, but still modest, positive and statistically significant effect on social trust. The effect is more pronounced for individuals with poorly educated parents. The positive effect of detracking reforms goes hand-in-hand with more understanding attitudes towards persons with a different background than one’s own. The lack of a clear effect of reforms that extend compulsory schooling on social trust reinforces the findings of recent single-country studies that have been unable to confirm a causal effect of education on social trust. However, the effect of detracking reforms, albeit modest, shows that education can have a positive effect on social trust but that the institutional character of education may be a conditioning factor.