This report presents the results of two field-based experimental studies to determine the effects of questioning techniques on student achievement and attitudes. The first study was done to determine what student learning outcomes are affected by teachers' use of probing and redirection techniques in classroom discussions. Another purpose of the experiment was to determine the relative effect on student learning of teachers' questions delivered in both oral and written formats. The second study was conducted to determine what student learning outcomes are affected by variations in teachers' use of higher cognitive questions. These questions require the student to state predictions, solutions, explanations or opinions, expanding on information presented in the curriculum and interpreting it in his own way. This experiment was designed to test the belief that use of higher cognitive questions is important for developing students' ability to think. The finding of both studies was that discussion following critical viewing and/or reading of curriculum materials was effective in promoting student achievement. Writing responses to questions appeared to develop knowledge acquisition as effectively as participation in discussion. However, written exercises seemed less effective for improving higher cognitive response ability than oral discussion in which the students' responses are probed and redirected by the teacher. The methodology of the experiment is described in detail, and five appendixes list the statistical results of the two studies. (JD)