This article describes a study designed to explore sources of influence on the judgments made by science teachers on school characteristics, classroom features, and properties of a science curriculum. The study had its theoretical basis in the concept that members of a social organization operate under certain functional paradigms, which govern their approach to events within the organization, and particularly to the implementation of innovations. Empirically, the study formed part of the Canadian contribution to the Second International Science Study, and was based on a survey of some 2000 Canadian teachers. The survey used an adaptation of policy capturing methodology, in which teachers were presented with variations in a hypothetical scenario designed to simulate a decision-making situation. Results suggest that teachers' judgments center around a number of factors, the primary ones being concern for student ability and interest, teaching methods, and school spirit and morale. On the other hand, variations in the scientific basis of a curriculum appear to exert little influence. The results are interpreted as indicators of the major elements of teacher functional paradigms.