From the colonial period to the present, no form of integration (defined as the opening of institutions and communal spaces to members of different groups) has produced more conflict than the integration of American schools. Struggles to open other locations within the social landscape--such as railroad cars, buses, restaurant counters, and water fountains--have sparked similar battles, but they have never been so persistent, nor so passionate, as those fought over the schools. The combination of large-scale government outlays with the prospect of sustained intimacy between young people has proven a sure formula for heated confrontation. Yet, despite the attention that has been devoted to it, historians have treated educational integration on rather narrow terms, approaching this cultural phenomenon almost exclusively as an issue of racial inclusiveness. This article makes the case that educational integration in the United States has a much longer and more complex lineage than previously recognized. The author suggests that the process did not begin in the middle of the twentieth century, but in the middle of the eighteenth, and that it began with religion rather than race. He traces the early history of religious integration in American schools, as well as positing some preliminary conclusions on the relationship between this and other forms of educational integration.