BACKGROUND: Despite evidence of school effects on drug use, little is known about the social and institutional processes through which these may occur. This study explores how school experiences may shape young people's drug-related attitudes and actions and adds to existing evidence highlighting the importance of drug use in young people's identity construction and group bonding. METHODS: Case study qualitative data were collected through semi-structured interviews supplemented with observations. Fourteen students aged 14-15 were interviewed in autumn 2006 and again in summer 2007. Five teachers were interviewed. RESULTS: Inner-city secondary schools may constitute risky and insecure environments, and thereby act as structural forces in shaping how students form peer groups and respond to feelings of insecurity. Cannabis use--and identities constructed in relation to this--appeared to play a key role in how students manage insecurity. Black and dual-heritage students formed large, 'safe' ethno-centric school social networks and smoking 'weed' appeared to be an important source of bonding and identity. For some students, a vicious circle may exist whereby the process of 'fitting in' exacerbates difficult and conflicting relationships with teachers and parents, entrenches disengagement from education and leads to further cannabis use. There also appeared to be a diffusion of this 'safe' identity construction beyond these disengaged students. Cannabis and other drug use may also be an important safety strategy and source of bonding for pro-education students who need to be seen 'getting high' as well as 'aiming high'. While some students constructed 'safe' and 'sweet' identities others were constrained by their position and resources at school. CONCLUSION: Inner-city schools may both reflect and reproduce existing patterns of drug use. The concept of risk hierarchies may be important when designing and evaluating school-based drug-prevention strategies.