Most previous research on the social organization of schools neglects to consider that such organization may vary depending on several factors, including size, staff composition, and environment. This study utilized two images of school identified by Corwin: the rational bureaucracy (formally organized social structure in which activities have clearly defined patterns and are closely related to goals) and the natural system (social structure in which individual actions are not clearly related to organization goals, and there is little interdependence or centralized control). Data were collected from 13 elementary, junior high, and high schools by a questionnaire returned by 638 nonadministrative professionals. Three characteristics were identified that distinguish between rational bureaucracies and natural systems: goal consensus, centralization of control, and extent of coordination. Contrary to expectation, elementary schools correspond best to the rational bureaucratic image, and high schools conform more to the natural systems image, with junior high schools in between. Further analysis suggested that the rational bureaucracy also correlates with small school or district size, a predominantly female, less educated staff, with high turnover, and substantial central office influence. (JM)