Rather than concentrating on similarities, it would seem far more profitable to search for ways in which schools are unlike other organizations or the models we have of these. It was suggested that we need to begin building images of schools that are congruent with their reality. This paper attempts the first stage in the task by identifying major generic characteristics of schools in general and public schools in particular. The generic characteristics of schools in general are pupils, classes, instruction, teachers, curriculum, and authorities external to the school itself, which is located on specialized premises. Ideal-type public schools are distinguished by external authorities that form part of a hierarchically organized administrative structure in a sovereign state and compulsorily enrolled pupils that are permanently resident within the territorial jurisdiction of the state. Comments are restricted to two implications for administrative theory and two possible uses in organizational analysis. (Author/MLF)