The objective of this study was to provide insight into the relationships between the teachers’ and students’ language usage, the MTB-MLE policy implementation, and student reading outcomes, especially in areas with linguistically heterogeneous populations. It sought to examine how language usage in the classroom conforms to or diverges from the MTB-MLE policy after six years of implementation, which factors are associated with higher policy implementation, and how language usage by teachers and students relates to student learning outcomes.