God's place within the public schools of the United States has been debatable, and subject to controversy, for as long as there have been public schools. In colonial America, religion played a central role in the schools of every colony, but the understanding of religion differed substantially from colony to colony. With the coming of nationhood and the separation of church and state on the federal level, the public school was pressed into service as a new kind of national church, commissioned to create and carry the common culture and morality of the nation. Since citizens differed dramatically in their definitions of this culture and morality, and especially since newly arrived Catholics, newly freed African Americans, and newly conquered Native Americans all had still other ideas, the content of the nation's common creed – and especially the appropriateness of its more overtly religious dimensions – was a subject of fierce debate and continuing change throughout the nineteenth century.

By the end of that century, due as much to exhaustion as any thoughtful will, schools had dropped the more obviously religious – and generally Protestant Christian – trappings of the school faith, replacing them with a generic commitment to democracy reinforced by a set of patriotic symbols, including flags and flag salutes and the omnipresent pictures of George Washington and Abraham Lincoln. Some religious symbols – bible reading and prayer in a minority of states, Christmas carols and pious references in most communities – continued well into the twentieth century.