This study explored how learners apply their understanding of geometry to visualise and analyse the properties of 2D shapes. This paper uses Van Hiele’s theory as a theoretical framework. The research design for this study employs a mixed-method approach. A content analysis is used for qualitative research methodology, whereas descriptive statistics is used for quantitative research methodology. 429 learners were assessed in total. With grade 6 (n=271) learners and grade 9 (n=157) learners assessed. The research includes five primary schools with grade 6 classes and two secondary schools with grade 9 classes. The assessment of grade 6 and grade 9 learners is based on their understanding of 2D shapes and geometric knowledge, using the grade 6 level of assessment. The study examined the geometric knowledge performances of grade 9 learners compared to grade 6 learners. It aimed to understand the grade 9 pre-existing knowledge of the properties of 2D shapes. The analysis of the performance results for 2D shapes reveals that grade 6 achieved a much greater percentage of 69.7% compared to the average, while grade 9 obtained an average rate of 56.7%. These findings indicate that the level of pre-existing knowledge of 2D shapes among grade 9 learners is inadequate, and this can be linked to a lack of conceptual knowledge in their earlier grades. The study suggests that educators should employ a pedagogical method that fosters conceptual knowledge, in order for learners to attain and fulfil the geometric understanding required at each Van Hiele level.

Keywords: Visualisation, 2D shapes, Van Hiele, conceptual knowledge, geometric knowledge.