Over the past decade, there has been greater attention placed on the potential value of peer support models, particularly in school contexts. This paper uses the case study of an Irish school-based peer mentoring programme to identify the added value that peer led models of social support for children and young people offer in a school setting. The Irish national youth organisation, Foróige, runs the Big Brothers Big Sisters school-based mentoring programme in over 60 Irish secondary schools, with the aim of improving young people's transition to secondary school. Qualitative research was undertaken with 36 principals and teachers in secondary schools operating the programme. Five specific ways in which the peer mentoring model adds value to existing support in schools are identified and discussed, while challenges associated with the model are also highlighted.