Are students with special educational needs excluded from the reform promise of "mathematics for all"? This paper explores the discursive production of students with special educational needs in the context of professional development (PD) for collaborative problem-solving teaching. We held interviews with Chilean primary school teachers after their participation in PD and used a post-structural analysis to examine them. We turned to policy and institutional practices to understand the disability discourses that were evident. Teachers called on medical and deficit discourses to produce these students as abnormal and problematic in their learning of mathematics. Yet teachers also blurred the lines of categorisation between and within labels of special needs, including other students in these terms. Simultaneously, the reform PD created space for a counter discourse of ability. We suggest PD should help teachers of mathematics resist deficit discourses and see the ways in which experience may run contrary to them.