Background: Given the lack of research into English language instruction in multilingual contexts, this study explored the switch from mother tongue to English in a South African township school. Aim: This study aims to find out how teachers and parents view the implementation of English as a medium of instruction. Setting: The study was conducted at a multilingual township primary school that implemented an English-medium instruction policy from the foundation phase. Methods: A case study approach was applied to this qualitative research study. Semi-structured interviews were conducted with four foundation phase teachers and three parents of learners. In addition, observations of the classes of the selected teachers were made, and the data were analysed thematically. Results: The findings suggest that the English medium of instruction poses barriers to effective learning and teaching at the foundation phase. For most township learners, English is not the dominant language in their everyday interactions, and they have limited contact with the language outside the classroom. In addition, most teachers struggle to use English as a medium of instruction. Conclusion: Although some schools have shifted to an English medium policy, the decision appears ill-conceived because its success is insignificant in South Africa, where English is the first additional language for most learners and teachers. Contribution: The findings offer a research framework formulated by integrating past literature, and a theoretical framework for understanding the English medium of instruction where learners are exposed to multiple languages.