Theory and research supports the implementation of cognitive and behavioural interventions (CBI's) to address social, emotional and behavioural difficulties (SEBD) in children. The literature argues that schools are an ideal place in which to implement such interventions. As part of a county initiative, school staff were trained and offered follow up support by 2 Educational Psychologists (EPs) around the use of school-based CBI to support children who have SEBD. The 10 participants (from 5 schools) in this research were part of this initiative: they received 4 sessions of training followed by either monthly individual supervision, or group supervision, around their use of CBI. Training and supervision targeted implementation of key CB competences, selected from a competency framework recommended by 'Improving Access to Psychological Therapies' (IAPT, 2011). The research explored staff perceptions around the CB competences that they implemented, their methods of implementation and the barriers and facilitators to their implementation. The research used a mixed methodology design. Qualitative data was analysed using thematic analysis and quantitative data was analysed using descriptive statistics. Data was gathered through interviews, supervision sessions, intervention diaries and training evaluations. Exploration of facilitators and barriers to implementation was based on Durlak and DuPre's (2008) model of intervention implementation. Facilitators/barriers discrete from this model were also identified. Identification and exploration of such factors can assist in ensuring quality implementation of school-based interventions in the future. This study demonstrates how school staff can implement a range of CB competences and through multi-levels of intervention in schools. The potential role of the EP in supporting school staff to implement CBI is also discussed.