After reviewing effective teaching research during the past 20 years, one basic question arises: do teachers make any difference? Specifically, do teachers' classroom practices have any effect on student outcomes beyond the effects of ability and home background? What knowledge of minimal teaching competencies has been gained, and how firm is the knowledge base? Attempting to address these issues, this paper reports the results of a year-long classroom observation study involving 75 second- and fifth-grade teachers. Outcome measures included reading and mathematics achievement, student self-concept and classroom social status, and classroom behavior ratings. Teacher perceptions were measured through Q-sort, questionnaires, and indepth interviews. The study focused on the"commonplaces" of teaching, including content coverage, time usage, student-task engagement, group and individual instruction, question-response sequences, and student discipline. Results suggest that achievement is maximized by the following classroom conditions: high emphasis on academic instruction and student engagement in academic tasks, whole class instruction, effective question-answer and seatwork practices, minimal disruptive behavior, and prompt feedback to students. While little relationship between teaching variables and student achievement can be proven, the above recommendations are low-cost and worth trying. (MLH)