Peer support approaches, where pupils offer formal support to others, are used in schools as an additional source of pastoral care. Previous research shows benefits for whole school environments, pupils who receive support, and pupil peer supporters, but is largely limited to Western case studies, which are often short-term and/or limited to qualitative data. This thesis addresses these issues through cross-national work on peer support use, and longitudinal case studies. Peer support use in Japan was investigated through a qualitative study. A range of approaches was seen and major themes identified, including the evolution of Japanese peer support, conflicts in approaches, and an emphasis upon community. A qualitative study in South Korea explored peer support and other anti-bullying initiatives, both proactive and reactive. Thematic analysis showed the importance of collectivist values, and a gap between policy and practice. Peer support was little used and, despite positive attitudes, barriers were perceived. A comparison of the UK, Japan and South Korea considered the impact of cultural values, education systems and the nature of bullying upon peer support use. Two mixed methodology case studies of peer listening schemes in UK secondary schools were conducted, one over 18 months and another over six months. Both schemes had the general aim of providing additional pupil support, without focus on particular outcomes. Impact upon the domains typically benefited by peer support was evaluated; findings were broadly similar. Pupil awareness of the service was high, but in-depth knowledge was weaker and use was low. Attitudes were mixed, impact upon bullying and school climate was limited, but users and peer supporters perceived benefits. Both schemes evolved to include multiple approaches, and practical factors affecting development and effectiveness were identified. Finally, implications for peer support practice are drawn from the findings as a whole, and future research directions suggested.