Using the psychological framework of rational-emotive behaviour therapy, the principal aim of this study was to establish whether irrational beliefs, self-efficacy or pupil behaviour predicted teacher reports of stress. A secondary aim was to establish whether these variables, in addition to teachers' verbal feedback to pupils in class, predicted on-task pupil behaviour. Participants consisted of 58 teachers from five secondary schools, who completed three self-report questionnaires examining teacher stress, self-efficacy and irrational beliefs. In addition, both teachers and pupils were systematically observed in class using a structured schedule. The results indicated that high self-reported irrational beliefs and low self-efficacy predicted high levels of teacher stress. In addition, high self-efficacy and low levels of negative comments directed at pupils' social behaviour and academic work in the classroom predicted high levels of on-task pupil behaviour. The implications for supporting teachers in these areas are discussed. (Contains 4 tables and 2 figures.)