Grounded in sociocultural theory, this study uses an ecological approach to examine how student interactions within a dual-language school context may offer affordances for increased linguistic and conceptual understanding. Using qualitative analysis of student discourse, this paper focuses on data from recorded interactions between pairs of fifth-grade students engaged in writing activities (in English and Spanish). Findings demonstrated that the following key contextual factors cultivated a space for languaging (Swain, 2006), and thus enhanced conceptual understanding: 1) the interplay of two languages as academic tools; 2) the recognition of learners' expertise and distinct linguistic funds of knowledge; 3) opportunities for co-construction; and 4) student and teacher strategies that call attention to language. This study has implications for the education of language-minority students in English-medium classrooms and suggests that teachers should cultivate learning spaces that draw upon their students' other languages in order to promote a deeper analysis of English. This study urges future research to more closely consider reciprocal affordances for language learning among bilingual learners and seeks to bridge insight across the fields of second language acquisition and bilingualism. (Contains 2 tables and 8 footnotes.)