Language as a Mediator of Learning: A Bayesian Multilevel Analysis of Multilingual Mathematics Classrooms in Zambia

Abstract

Kadonsi Kaziya

Persistent linguistic inequalities continue to constrain mathematics learning in Zambia, where learners transition from familiar local languages to English as the medium of instruction. This study investigated how language functions as a mediator of learning across learners, classrooms, and schools using Bayesian multilevel modelling. A cross- sectional sample of 1,284 learners nested within 54 classrooms and 18 schools completed assessments of L1 and L2 proficiency, working memory, mathematics achievement, and measures of classroom language practices and school- level multilingual support. Four hierarchical Bayesian models were estimated using MCMC procedures with weakly informative priors, model comparison via WAIC/LOOIC, and posterior predictive checks. Results demonstrated strong evidence that L2 proficiency (β = 0.42, 95% CrI > 0) and L1 proficiency (β = 0.18, CrI > 0) significantly predicted mathematics achievement, with working memory exerting additional cognitive influence. Supportive teacher language practices translanguaging, strategic code-switching, L1 explanation, and learner talk—yielded robust positive effects, including cross-level interactions showing amplified benefits for learners with low English proficiency. Linguistic coherence and teacher–learner L1 match positively shaped performance, whereas linguistic diversity produced negative effects only in classrooms lacking multilingual scaffolding. School-level policy implementation, availability of local- language materials, and institutional support for multilingual pedagogy exerted indirect impacts through classroom practices. Findings affirm that language is a powerful mediator of mathematical understanding across ecological levels. Strengthening linguistically responsive pedagogy, classroom discourse, and institutional language-in-education practices is essential for improving mathematics learning in multilingual systems.

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