Following Snow's (1973) description of an "inductive" process of theory formation, this article addresses the organization of the knowledge base on school effectiveness. A multilevel presentation stimulated the conceptualization of educational effectiveness as an integration of system-level, school-level, and classroom-level factors. Next steps in theory formation, based on the formation of broader constructs and eclectic use of available theories, are considered in a confrontation with different appreciations of the strength of the current knowledge base. It is concluded that a range of different interpretations of the rationality paradigm (synoptic planning, contingency theory, creating market mechanisms, and cybernetics) does rather well in explaining both positive and negative outcomes. Alternative theories like loose coupling and self-organizing enlarge the scope of potentially effectiveness-enhancing factors as well as variables and mechanisms associated with ineffectiveness.