Language: a cultural capital for conceptualizing mathematics knowledge

Mathematics education in South Africa is in crisis. Students continue to perform at a lower level compared to other nations including those with low GPD compared to them. Two factors have been highlighted in research that impedes mathematics learning: teacher content knowledge and irrelevant teaching strategies. This study contributes to this literature by investigating five African (from a former White school) fifth grade students' learning of length measurement with the aim of eliciting the students' thinking levels by using a length learning trajectory. Clinical interviews and teaching experiments were employed for a comprehensive description of these students' processes. The findings reveal that students' mother tongue is a psychological tool that enriches their mathematics learning process, learning trajectory assisted in analysing students developmental processes with language and poor number development impeded abstraction in learning of length measurement concepts.