Mother tongue-based education has been central to the promotion of early literacy skills in many multilingual contexts of the Global South. However, learners in such environments may face significant linguistic challenges when changing language of instruction during schooling. In particular, the linguistic distance between mother tongue and official language may be a significant barrier to learners. This paper provides an empirical approach to this issue by employing language matching based on linguistic distance between languages to explore changes in literacy scores for learners who change language of instruction. Findings show that the greater the linguistic distance between two languages the larger the loss in foundational literacy. We conclude that language matching could be introduced as a tool to identify at-risk learners during transitions and, if possible, as a tool for linguistic allocation of students who have the possibility of selecting between schools with different languages for instruction.