This paper criticizes the work of Barak Rosenshine on the effects of teachers on student achievement. The author cautions against accepting Rosenshine's generalizations on teaching techniques. He makes the specific criticisms that Rosenshine a) did not operationally define student achievement, b) did not assess the validity of the student achievement measures used in his work, c) did not determine whether the achievement measures were appropriate to the students sampled, d) did not determine whether or not achievement measures were related to the curriculum objectives of the teachers, and e) combined the results of various studies without examining the relationships among them. Further, the author makes recommendations for future research on the topic. (JB)