This report focuses on current attempts by researchers to examine teacher effectiveness through the "task hypothesis," which asserts that effective teachers accomplish a large and diverse set of tasks--or discrete, goal-oriented units of work--in their classroom. After an introductory critique of past efforts to assess teacher "traits" or "behaviors," the report defines task analysis, suggesting that it is better able to examine the appropriateness of teacher behavior in context than past attempts at categorizing and evaluating teacher behaviors or qualities. Eight major teacher tasks are then described, along with current research findings about their importance: (1) planning instruction; (2) assessing students; (3) clarifying behavioral rules and routines; (4) organizing the classroom; (5) creating a learning set; (6) teaching to objectives; (7) providing for student practice; and (8) maintaining student involvement in learning and disciplining inappropriate behavior. Finally, four examples are provided of school districts that are putting the research on effective teaching into practice. Selected references are included. (TE)