South Africa is a multilingual country with eleven official languages, yet English remain the dominant languages of learning and teaching in most schools. This creates a disadvantage for learners whose home languages are African languages, particularly in science subjects like Physical Sciences. While previous research has focused mainly on helping learners cope with English, there is limited attention on how learners and teachers use home language to support learning and conceptual understanding in science classrooms. This study explores the role of home language during Physical Sciences lessons in a multilingual Grade 12 class in a township school in Gauteng province.

This qualitative case study focused on how both learners and their teacher used home language to engage with scientific concepts during two Physical Sciences lessons on the photoelectric effect topic. The class consisted of 24 multilingual learners who spoke mainly isiZulu, isiXhosa, and Setswana. Data were collected through video and audio recordings of small-group discussions and whole-class interactions. Learner talk was analysed using Mercer’s framework of exploratory, cumulative, and disputational talk. The teacher’s use of home language during classroom instruction was examined through the Initiation–Response–Feedback (IRF) model. Additional insights were gathered through field notes and observation.

Findings show that learners predominantly used their home languages during exploratory talk, which involved reasoning, challenging views, and justifying scientific ideas. This form of engagement supported deeper conceptual understanding. Code switching and transliteration were commonly used to bridge language gaps, especially where no equivalent scientific terms existed in African languages. The multilingual nature of the classroom enabled meaningful peer interactions, particularly among learners who spoke the same home language. However, in mixed-language groups, language barriers occasionally hindered communication, leading learners to adopt township slang or hybrid language forms to continue participating.

These findings suggest that while multilingualism enables learners to access and express scientific ideas using languages they are most comfortable with, it also introduces communication challenges when group members do not share the same home language. In such cases, learners may struggle to follow each other’s reasoning, which can limit their participation or lead to misunderstandings. Therefore, there is a need for intentional grouping of learners based on shared linguistic backgrounds to promote clearer communication and collaboration. Additionally, teachers should adopt facilitation strategies that support multilingual interactions—such as encouraging translanguaging, using bridging questions, or providing key scientific terms in multiple languages—to ensure that all learners are able to meaningfully participate in group discussions and develop conceptual understanding.

Keywords: Home Language, Multilingual classroom, Classroom Talk, Physical Sciences, Township schools.