Learner diversity should be understood beyond the aspects of race, culture and gender. Learner-centred practices have been highly acclaimed as practical tools to meet learner needs in diverse classrooms. The purpose of this research is to determine whether mathematics teachers can employ assessment to monitor and encourage learner diversity in their classes. Assessment for learning techniques, as per research evidence, has the ability to assist teachers to improve their teaching practices. The article does this by referencing research in which Grade 6 mathematics teachers employ assessment for learning to improve the quality of mathematics teaching and learning. For this purpose, interviews, non-participant observations and document analysis were used from selected teachers to understand teachers' beliefs about assessment for learning and actual classroom practices. The non-participant observation was conducted in classrooms of different primary schools. Nine mathematics teachers were conveniently sampled from township primary schools in Gauteng as the study participants. The study's findings revealed that teacher-centred assessment approaches still dominate mathematics classrooms. Furthermore, it could be deduced that mathematics teachers have classroom assessment challenges that hinder the promotion of learner diversity as it relates to assessment practices. Therefore, the study provides an understanding of the role of a teacher in responding to learner needs and academic development in mathematics through assessment for learning. Contribution: The research contributes to primary school mathematics teaching by focusing on the practical undertaking of assessment for learning and its relevance in meeting the diverse needs of learners.