Across countries, social inequalities exist in citizens’ democratic engagement. One potential channel through which these gaps are formed concerns schools, yet little research has yet considered the relation between schools’ supply of democratic education and social inequalities in students’ democratic outcomes. This study examines whether schools’ supply of democratic activities moderates the relation between students’ social background and their intended political participation, civic knowledge, and civic self-efficacy. Based on multilevel path analyses using ICCS 2016 data from 15 European countries, results confirm social inequalities in students’ democratic outcomes, and a positive indirect role for schools’ supply of democratic activities, via students’ participation in them. Schools’ supply does not depend on their social student composition, nor do we find strong support for a moderating role of supply for the relation between students’ social background and their democratic outcomes. Students with advantaged social backgrounds report higher participation in democratic activities as offered by schools, and the social stratification of some democratic outcomes is stronger among students who participate more in democratic school activities. This suggests that equal supply of democratic activities by schools is unequal in its reach, which we discuss in relation to the accessibility of activities for students.