Research on classroom teaching is discussed within the conceptual framework of the analysis of student classroom tasks. Three types of learning tasks are illustrated: understanding; memory; and routine problem-solving according to an algorithm. It is contended that most classroom research projects study teachers' and students' actions, rather than learning tasks; it is assumed that learning is taking place as a result of these actions. Furthermore, there is more emphasis on how much is learned than on what is learned. Two important questions concerning teaching models are discussed: what are the actual tasks posed for students and teachers in classrooms?, and why do these tasks exist? After discussions of classroom task goals, ambiguity and risk concerning task accomplishment, and the role of students and teachers, three conclusions are presented: (1) there is not a direct cause-and-effect relationship between specific teacher behavior and student achievement, rather, teacher behavior is shaped by interaction with students; (2) learning tasks directly shape achievement; and (3) learning tasks do not always take place in the classroom. (GDC)