The transition from primary school to secondary school can be a difficult time for young people, yet little is known about what schools do to support the social, emotional and mental wellbeing (SEMWB) of their pupils during this period. The purpose of this research is to explore the ways in which an urban Scottish secondary school and two of its local feeder primary schools attempt to support their pupils' SEMWB as they make this transition. A case study design was adopted to create a rich and situated account of teachers' experiences and perceptions about transition approaches through semi-structured interviews. Participants were teachers in the secondary school, a large primary school serving a relatively affluent area and a smaller primary school in a more diverse, less affluent area. Thematic analysis of the data, led to the identification of three inter-connected themes underpinning the ability of schools to support their pupils' transition effectively: positive relationships, positive communities and positive environments. This suggests that teachers adopt a broadly socio-ecological perspective, viewing transition as a multi-faceted process, in which not only individual pupil characteristics but also social, cultural and relational factors are important. However, within this broad framework, teachers' precise understanding of SEMWB varied within and across contexts, suggesting the importance of leadership and of a shared understanding, both within each school and across a cluster of schools. Teachers should also be supported to evaluate their initiatives and the impact these have on transition.