Language diversity in South Africa continues to problematise educational provision and the realisation of equitable educational opportunities for all learners in various ways. This article presents the findings of ongoing research which explores the effect of language in education policy on the L1 and L2 proficiency of Grade 7 learners in township schools in Gauteng Province, South Africa. This study compares three subgroups of Grade 7 Xitsonga speaking learners in three respective township schools in terms of English (language of learning and teaching) and Xitsonga (home language) proficiency as determined by standardised testing in two domains: reading and writing. The research is done against the background of language policy in South Africa and is embedded within the theoretical framework of bilingual literacy, additive and subtractive bilingualism. Results indicate there were no significant differences between the reading and writing performance in both L1 and L2 among the subgroups of learners in the three respective schools. Although learners performed somewhat better in writing in both L1 and L2 than reading in L1 and L2, this performance was still sub-standard. This suggests that for these learners bilingualism is largely subtractive which could be attributed to short term exposure to schooling in L1 and low levels of exposure to English outside the classroom.