A mathematics teacher's response to a dilemma: 'I'm supposed to teach them in English but they don't understand'

Background: English is the dominant language in South African schools although it is the home language for less than 10% of the population. Many schools have yet to embrace the Language in Education Policy's advocacy of additive bilingualism. This has led to a majority of the country's children learning and being assessed through a language in which they lack proficiency. Aim: This article draws on second language teaching and learning theory to make a case for more systematic support for learners' second language development and for legitimation of use of home language in mathematics classrooms where a different language is the official medium. The article shares empirical data from a South African Grade 4 mathematics teacher's classroom to illuminate arguments in favour of additive bilingualism. Setting: A non-fee-paying public school in Eastern Cape province of South Africa. Methods: Data were collected through lesson observations, teacher interviews and assessment data generated by a professional development project initiative. Results: The 'illuminatory' lesson data suggest that allowing learners to use their home language alongside English facilitated their mathematical sense-making. This suggestion is strengthened by assessment data from a larger development project mandated with exploring ways for improving the quality of primary mathematics teaching and learning. Conclusion: Insights from this article add to many other calls made for more sustained and serious consideration of the pedagogical and epistemological value of multilingual approaches for South African classrooms.