Background: The NECaSP intervention aspires to increase sport and physical activity (PA) participation amongst young people in the UK. The aims of this paper are to report on a summative process evaluation of the NECaSP and make recommendations for future interventions. Methods: Seventeen schools provided data by students aged 11-13 (n=913), parents (n=192) and teachers (n= 14) via direct observation and questionnaires. Means, standard deviations and percentages were calculated for socio-demographic data. Qualitative data was analysed via directed content analysis and main themes identified. Results: Findings indicate further administrative, educational and financial support will help facilitate the success of the programme in improving PA outcomes for young people, and of other similar intervention programmes globally. Data highlighted the need to engage parents to increase likelihood of intervention success. Conclusions: One main strength of this study is the mixed-methods nature of the process evaluation. Changes in the school curriculum can be successful once all parties are involved (community, school, families). Finally it is recommended that future school based interventions that bridge sports clubs and formal curriculum provision, should consider a more broad approach to the delivery of programmes throughout the academic year, school week and school day.