This paper focuses on the discursive characteristics of peer assessment interactions, drawing upon recent research into formative assessment within a task design involving extended project-based work tackled in groups by pupils. Case studies were conducted within two schools in socially-deprived areas of Scotland. They included classroom observation, digital video and audio data collection, and a series of interviews with pupils and teachers. The task design created opportunities for interdisciplinary, collaborative learning and generated strong pupil engagement. However, a disjuncture is seen between the conflictual characteristics of peer assessment, which are suggested to have gendered and social class dimensions, and the discourses of teamwork and community-building that were privileged in the classrooms observed. Although recognised more in research conversations, the article argues that teachers could be better supported in considering how social class and gender are implicated in peer assessment and in developing classroom discourse that addresses social equity issues.