The language used as a medium of instruction (MOI) has implications for learning outcomes. In most African classrooms, an international language is solely or dominantly used as an MOI. There is a debate about how this practice is associated with students' learning outcomes. This study uses Zambian PISA for Development 2018 data and school fixed effects to examine how the degree of teacher code-switching and the use of student home language in specific pedagogical situations (explaining complex concepts, engaging students in discussions, and students struggling to learn the curriculum) are associated with learning achievements. Findings suggest that these practices are not associated with learning achievements, and implications of the findings are discussed.