Our theoretical framework allows us to consider the mathematics class as a School Mathematical Discursive Community, relying on Bakhtin's theory of genres of discourses and heteroglossia. In our paper, we question how the teacher can orchestrate heteroglossia in order to establish a Relevant School Mathematical Discursive Community. We show that such an orchestration, which relies on a secondarising process, is productive for teaching and learning mathematical concepts (in this case, decimals and fractions) at primary school.