The poor learner outcomes in the TIMSS assessment, the SACMEQ assessment, and the Grade 9 ANAs led to this study being conducted. The purpose of the study was to explore whether Grade 9 mathematics teachers’ teaching can improve learner outcomes. This study therefore investigated the literature regarding mathematics teachers’ classroom practices with an emphasis on teachers’ Pedagogical Content Knowledge (PCK), Pedagogical Content Knowledge and Skills (PCK&S), and how these teachers used assessment outcomes to inform their teaching of mathematics. In developing learners’ conceptual understanding and higher-order thinking skills, mathematics teachers not only need subject matter knowledge, but also PCK and the skill to implement their planning efficiently during instruction. The conceptual framework for this study is based on Gess-Newsome’s (in Berry et al., 2015) Model of Teachers’ Professional Knowledge and Skills. Based on this, PCK was examined in the planning and executing of topic-specific instruction and as a skill when teaching this content to the learners for enhanced learner outcomes. The research approach was qualitative and the research design was a case study. Two Grade 9 mathematics teachers from one school were selected through purposive sampling. The data were collected using a baseline test, three classroom observations, one semi-structured interview and a formative test. Both teachers used Direct Instruction in all their lessons, but proficiently used various representations when explaining the work, and integrated the topic into other mathematical topics and real-life scenarios. The teachers admitted that they did not usually make use of baseline tests to inform their teaching due to time constraints, but found it valuable during this endeavour. The findings from the two tests showed many learners still have the same misconceptions regarding the concepts of surface area, volume and capacity; continued to make the same typical mistakes in finding formulae for surface area and volume; and still found it difficult to convert between the SI units. There was, however, significant improvement in learner outcomes, but the positive outcomes regarding all typical mistakes and learner difficulties were still below 46%.