This study evaluated the effectiveness of a lecture on behavior modification techniques given to three elementary teaching staffs that were volunteered by their principals. It was expected that the group lecture would result in significant increases of teacher compliments and decreases of teacher reprimands even though the teachers did not request the lecture directly. These changes in teacher response to student behavior were then expected to be reflected in increases of the percent of students observed to be engaged with the assigned task in each classroom. Thirty-four teachers selected randomly from three elementary schools were observed for ten minutes one week before and three weeks after receiving the behavior modification lecture. The results indicated that the rate of teachers' compliments increased and reprimands decreased significantly following the lecture on behavior modification. The results, therefore, indicate that students' classroom functioning can be changed by teachers' application of behavior modification techniques. (Author)