Social system perspective which belongs to systems theory has been elaborated comprehensively using its founders' ideas, and characteristics of schools have been explained consulting to this perspective. The course of social system idea has been reviewed along with its relation to other systems. How researchers who assumes schools as social systems define the main components of the school has been reviewed. By attaching importance to the humane side of school, social systems perspective differentiates school from for profit organizations. For this reason, social systems theory has been one of the most realistic models for schools. The assumptions behind this assertion are examined. It is probable that this perspective sheds light on research conducted in educational organizations.