Unique cross-national data on adolescents' civic skills, knowledge, and political attitudes are used to examine the democratic processes of modern mass schooling, effects of national political systems, and patterns of youth political socialization in 27 nations. Compared to the generally weak reported effects on mathematics and reading achievement, we find robust effects of schooling on youths' civics knowledge, skills, and attitudes. Secondly, there is empirical support for the importance of a supra-national political culture, beyond that of unique national cultures, in the political socialization of youth. Lastly, there is evidence of an emerging common polity among youth across nations. The results extend notions of the institutional influence of mass public schooling on the political socialization of youth. (Contains 4 tables and 5 notes.)