Twenty more effective and twenty less effective teachers were studied to determine if they differed in the ways they plan for instruction. The effectiveness of the teachers was determined by their ability to affect gains in reading and mathematics over two weeks of instruction with a specially designed curriculum unit. Four variables were noted as distinguishing between the planning of the more and less effective teachers. There were: (a) whether the teacher used specific or general information in planning; (b) whether the teacher believed students had the potential to learn the material; (c) whether the teacher considered the cognitive aspects of instruction; and (d) whether the teacher produced much of his or her own instructional materials. When the findings of this study were compared to the findings of a coordinated study of teacher and pupil perceptions of classroom interaction, two of the variables were found to be important in both teacher planning and classroom interaction. These two were teacher tendency to think in generalities rather than specifics, and teacher attention to cognitive aspects of lessons. (Author/JD)