This article focuses on using sociocultural theory to support student engagement with mathematics. The sociocultural approach used, collective argumentation (CA), is based on interactive principles necessary for coordinating student engagement in the discourse of the classroom. A goal of the research was to explore the affordances and constraints of using CA to enrich student engagement with mathematics. The design of the research was based on a teaching experiment that sought to capture the influence of social and cultural processes on learning and development. Participants included primary and secondary school teachers and their mathematics classes. This article focuses on the practice of one female primary school teacher. Data sources included interview transcripts, report writings, journal entries and observational records. Data were analysed using a participation framework. Findings suggest that aspects of CA such as students explaining and justifying ideas and presenting ideas to the whole class can be used by teachers to promote student engagement with mathematics.