Multilingualism is a complex phenomenon in the Pacific, particularly in Melanesia, where there is more than one language being spoken by individuals. Therefore it is important for the education systems to consider learners’ needs in providing quality education that accommodates students’ first language in the English curriculum. This study set out to explore teachers’ and students’ beliefs, practices and proficiencies in two selected secondary schools regarding their use of language in English classrooms. Bilingual/multilingual educational research is a recent phenomenon in the South Pacific, including the Solomon Islands. This presents serious considerations for policy makers, educational authorities, teachers and students about the importance of accommodating students’ first language (L1) alongside the English-only curriculum. A qualitative research methodology approach was used, based on the interpretive paradigm, with individual and focus group interviews and classroom observations. Eight teachers and sixteen students from two schools, one rural and one urban, were interviewed on their conceptions of language use and the place of vernacular, Pijin and English in the English curriculum. Classroom observations carried out on two of the teacher participants focused on their language practices in English lessons and on capturing students’ code-switching practices. The findings of this study suggest that there is a mismatch between teachers’ beliefs and practices. While all the teachers acknowledged the English-only policy, and the importance of using English as the medium of instruction, their reported practices and observed lessons supported the use of students’ L1. The students also highlighted that the use of Pijin and/or vernacular supported their learning of English. This raises important points regarding bi/multilingual educational approaches to teachers’ pedagogical practices in accommodating students’ L1 for effective learning purposes. This study has unveiled teachers’ beliefs about language use in secondary school classrooms, reported practices and students’ patterns of language use and assumed language proficiencies. It therefore makes a contribution to the Ministry of Education and Human Resources Development advocating for the importance of bi/multilingual education and teacher pedagogical practices and approaches to teaching English as a second language without impeding the students’ L1.