This paper uses sociocultural theories of language learning to investigate how teachers and students navigate between monolingual institutional policies and the multilingual realities encountered in a rural Kenyan fourth-grade classroom. The paper addresses not only how learners' communicative repertoires are deployed to make meaning in a foreign-language instruction context but also the sociocultural significance of these communicative practices. Results illustrate how the science teacher used heteroglossic practices to mediate students' access to literacy, hence, supporting the content learning and language development of students. Both the science teacher and the students preferred a more flexible use of language to make sense of their multilingual realities as opposed to monolingual view of literacy imposed on them by the language policy. I argue for the potential of heteroglossic practices in multilingual classrooms to ease the cognitive load of English language learners in the process of learning in an additional language. The findings highlight the need for legitimizing fluid language practices in multilingual classrooms in the process of acquiring an additional language and preparing teachers for a multilingual reality.