The purpose of this research was to investigate primary mathematics teachers' assessment practices in the context of the new integrated primary curriculum. This was a case study in which data were collected through classroom observations and interviews. Findings from the study revealed that teachers were able to use some of the assessment for learning strategies in their classrooms. These were communicating learning intentions and success criteria at the beginning of the lessons, making use of peer and self-assessment by learners. The study established that the use of success criteria can promote learners' self-reflective ability, regardless of their age. Findings also revealed that teachers were not providing learners with descriptive feedback that showed their strengths and weaknesses. Furthermore, the results of the study revealed that teachers encountered challenges in the implementation of assessment for learning in their classrooms. Some of the challenges encountered were a shortage of resources, high teacher--learner ratio, increased workload and reduced teaching time.