Pupils' behaviour can affect teacher morale, attrition, and exclusions. Teachers' efficacy beliefs can serve as a protective factor against stress and burnout. This study examined a possible association between teachers' collective efficacy (CE) beliefs and exclusion rates, and whether student-teacher relationships (STRs) affected CE beliefs and teachers' views about how they responded to difficult behaviour. A mixed methods design was utilised with four secondary schools in one UK local authority. A questionnaire ascertained CE beliefs. Subsequently, semi-structured interviews with ten teachers, with high and low CE, were conducted. A significant association was found between CE and the rate of fixed term exclusions. Interview data revealed four broad themes: The "Quality of Relationships"; the effects on "Efficacy Beliefs"; less "Reliance on Disciplinary Approaches" and having "Greater Tolerance". Positive STRs enable teachers to provide an environment in which behaviours are more respectful, reducing the need for disciplinary approaches, such as exclusion.