Drawing on a recent series of investigations into teacher information processing while teaching, a set of propositions to guide inquiry into the relationship between thought and action in the classroom are advanced. These propositions represent a "pre-theory"--steps toward defining the nature of information processing during teaching and the factors which determine its characteristics. The activity flow in a classroom so controls the kinds of information that teachers receive that they are very unlikely to process information in such a way as to move into a major decision-making frame. Teachers usually work within a general framework and "fine tune" that system. (Author/JD)