South Africa’s esteem is low with regard to current learner achievement in mathematics. Results from international studies, such as TIMMS and SACMEQ, continuously indicate that South African learners perform below international benchmarks in mathematics. Research and evaluation studies assert that teacher practices and poor early mathematics stimulation influence this state of affairs. Hence, this article reports on a study that explored the developmental progression of Grade R teachers’ mathematics knowledge and general knowledge of teaching participating in a professional development intervention. In this article I report on data collected after a two-day workshop conducted with the teachers. The video recordings of 14 teachers’ self-selected lessons were collected and transcribed, using a lesson observation tool, and analysed by means of thematic analysis. The findings indicated that teachers’ knowledge of number sense forms a strong foundation for improving the quality instruction of number knowledge. The first step seen to be taken by these teachers to engage the learners was the question and answer approach. The lessons of those who tried to let learners engage lacked structure and resulted in chaos. Demonstration and drill were used to develop the learners’ content knowledge. The teachers’ practices were inadequate as far as developing conceptual understanding is concerned; and their classroom management skills were not sufficiently developed to include all learners in their mediation. In instances where all the learners participated, the teacher directed the participation and did not allow for learner-to-learner engagement. It is crucial to note that they showed potential for growth and willingness to learn despite the limited or minimal the training they received.