Legitimation is suggested as a major function of schools in modern society and as a means of better understanding of the role that schooling plays in the development of society. The concept of "legitimation," as formulated by Peter Berger and Thomas Luckman is applied to analyze several historical and contemporary educational ideas which are utilized as legitimations of social conditions. Discussion is presented on the different levels of pre-theoretical and theoretical propositions. Two considerations are 1) that ideas about schools and schooling legitimate some aspects of the institutional order, and 2) that the institutionalization of education as schools and school systems legitimates from the point of view of the general public. For both the focus must ultimately be on ideas at the level of everyday or common sense knowledge because it is the general public for whom institutional arrangements and practices must be legitimated. Two supporting examples illustrate a) the role of educational ideas in legitimating gradations in status and income as an aspect of social order, and b) a way in which schools are legitimated in the eyes of the general public. A need for more extensive inquiry into legitimation is suggested. (Author/ND)