Using a cohort longitudinal design, this study examined pupils' perceptions of their teachers' classroom leadership, both before and after implementation of the Respect programme. Pupils in Grades 5-10 (age 11-16) in four Norwegian schools reported their perceptions of their teachers' emotional support, academic support, and monitoring five times over a period of five years. The results revealed increases in the pupils' perceptions of one or more of the three aspects of classroom leadership for all grade levels except Grade 9. Pupils in Grades 5, 7, 8, and 10 reported effect sizes larger than 0.20 for all three aspects. The largest effect size reported was 0.80, for increases in Grade 6 pupils' perception of teachers' monitoring. In order to rule out selection bias, which is a major threat to cohort longitudinal designs, pupils' reports of three measures of aggression were used as a control. The results indicated that there were no biases. (Contains 7 tables.)