Children are constructed as learners of mathematics by virtue of their participation within the classroom. Through its modes of measurement, discipline, sanctions and rewards, the discourse of mathematics classrooms make children visible as mathematically (dis)abled subjects. From this discourse “ability” emerges. Teachers transmit their own values and definitions of ability to their class. Children come to view themselves as learners of mathematics through the messages communicated by their teacher and through comparison with their peers. This study employs a mixed methods design approach (Teddlie & Tashakkori, 2009) across eight primary school classrooms at second and fifth class level in DEIS and non-DEIS schools. A total of twenty-four mathematics lessons were observed, while eighteen mathematics lessons were video recorded. Focus group interviews with children, child questionnaires and drawings were also employed in the data collection. Eight teachers and eight school principals were interviewed. This paper will examine the discourse around ability by drawing on the perspectives of teachers and children.