Using a sample of 384 Finnish teachers, in this study we explored how teachers' attitudes towards inclusive education, self-efficacy, and collective efficacy in behaviour management affect their behaviours in teaching appropriate behaviours to students, and how teachers' attitudes, self-efficacy, and collective efficacy mediate the effect of background variables on teacher behaviour. The results revealed that teachers' self-efficacy and collective efficacy significantly predicted their behaviour. The number of students with attention or behavioural problems has an indirect negative effect on teacher behaviour, mediated by teacher self-efficacy.