In this paper we report a qualitative case-study of how a primary school Principal enhanced staff belief in their efficacy and practice in relation to children's behaviour. Thematic analysis was used to analyse interviews with the Principal and teaching staff. We identified four main themes relating to their attributions, beliefs and practices: 'Attitudes and Expectations', 'Leadership', 'Communication', and 'School Ethos and Practices. We conclude by considering how the Principal's own beliefs and leadership practices were associated with changes in the beliefs and practice of the staff.