A report is given on research exploring the theory that stimulation from the teacher does not directly initiate student learning but activates cognitive processes that result in learning. Combined research into classroom processes and student information processing was conducted. An analysis of treatment theories that operate in research on teaching is presented. A description is given of the essential features of a cognitive model of student mediation, as well as an analysis of different types of academic tasks and their relationship to outcomes of instruction. The meaning students attach to classroom events and the way knowledge is gained from accomplishing classroom tasks is analyzed. A model of classroom tasks is applied to teaching effectiveness research to interpret existing findings and suggest directions for further research. (JD)