Schools have a seminal role in preparing a society's children for their adult responsibilities as workers, parents, friends, neighbors, and citizens. The United States, countries of the Organisation for Economic Co-operation and Development, Brazil, India, South Africa, and other multiethnic democratic nation-states have increasingly diverse demographic profiles that present challenges and opportunities for social cohesion. The focus of this chapter is the relationship between integrated schooling and social cohesion in nations such as these. The chapter's central thesis is that schools that are racially, ethnically, and socioeconomically diverse lead to educational outcomes that undergird the attitudinal antecedents to and structural conditions for social cohesion in multiethnic, democratic societies. Using the United States as a case study, the chapter synthesizes educational, social, and behavioral science research on the effects of school racial, ethnic, and socioeconomic status (SES) composition on various adult life course outcomes that are crucial to this condition. (Contains 1 figure, 1 table, and 10 notes.)