The primary-secondary transition presents both opportunities and challenges for children. For some, it may represent a 'critical period' which impacts their future mental health and well-being. This article focuses on identifying the affordances and constraints of a group-work approach to support children with social, emotional and behavioural needs (SEBN) across the transition with a specific focus on the socio-emotional aspects of transition. This evaluative, mixed-methods case study took place in six clusters of primary/secondary schools in Scotland involving 63 pupils who participated within support groups for around twenty 1-hour sessions. It focuses on the accounts of Support group Leaders, drawing from focus group discussions held within each cluster and a Likert-type scale questionnaire. A wide range of facilitators and barriers to implementation and to pupil progress were identified. Facilitators related principally to the quality of relationships and pedagogy which the support group afforded and the quality of support for the project. Barriers related principally to organisational and resource constraints and more general concerns around how behaviour support is perceived. The article argues that supporting the transition for pupils with SEBN is complex and there is no 'magic bullet'. Building a supportive infrastructure from the outset is key to success.