Check in-check out (CICO) is a widely used and studied behavioural intervention. Although CICO is an effective way to support pupils' behaviour in a school context, not all pupils benefit from basic CICO. A single-case experimental study was designed to evaluate the effects of CICO Plus support (CICO Plus) for participants whose behaviour was determined to be non-responsive to basic CICO. CICO Plus was planned and implemented with four pupils identified by school CICO teams as needing additional behavioural support. Individual CICO Plus support was planned by multiprofessional teams working on each pupil's case. The CICO Plus support was based on teaching social skills and behaviour at least three times a week in collaboration with families, schools and social and health care services. A concurrent multiple baseline design revealed increases in pupils' appropriate behaviour in their targeted behavioural goals and decreases on pupils' disruptive behaviour in school situations. Fidelity of the CICO Plus intervention and social validity among school personnel were also assessed. Results indicated that practical multiprofessional co-operation is essential to lay the groundwork for inclusive support for pupils at risk of severe problem behaviour.