Video tapes of similar lessons taught to small groups of students before and after science teachers attended a two-week curriculum workshop were studied to determine whether teaching style changed as a result of a workshop experience. The workshop had little influence on teacher's techniques. To develop a measure of the effectiveness of different teaching styles, the video tapes were viewed by large groups of students and their achievement, with report to the content of the taped lessons, was then measured. The workshop session did not change the effectiveness of the taped lessons in producing learning in other students, but there were differences in achievement between groups who viewed video tapes made by different teachers. Greater success was obtained when the taped teacher emphasized skills rather than content, concepts rather than data, and used analogies and compared ideas. (Author/AL)