In multilingual countries, debates about language policy in education persist. Many countries adopt a transitional bilingual approach in which children are taught to read in their first language (L1) as a subject before instruction shifts to an official language (L2) such as English. This model rests on the premise that L1 mastery aids L2 learning. Yet, most supporting evidence is correlational. We used an instrumental variable design to examine the causal effects of children's L1 reading proficiency on L2 reading development with data from 4,352 children aged 5–13 years in Ghana. Results showed that L1 reading proficiency positively impacts basic L2 skills such as letter–sound recognition, but the effect diminishes for decoding pseudowords and becomes nonsignificant for reading fluency, suggesting inconsistent cross-language transfer.
Moussa et al. (Fri,) studied this question.