As linguistic diversity is increasing in schools worldwide, research is needed to examine how to modify teaching and learning contexts in response to emerging multilingual students' different needs. Grounded in sociocultural theory, this study examined how teachers used discourse differently to respond to diverse students' needs as they participated in a language programme that brought together multicompetent language users, Spanish-expert students learning English, and English-expert students learning Spanish in secondary school. Analysing transcripts of student and teacher interactions, we identified discursive patterns that teachers used to mediate multilingual language-learning opportunities, to raise language awareness, and to cultivate a collective zone of proximal development in a linguistically diverse context. Findings shed light on the ways that teachers use languaging and translanguaging as mediational tools to gauge and respond to students' needs, while drawing upon students' funds of knowledge to deepen multilingual and multidirectional language-learning opportunities. Our findings have implications for how educators can differentiate their discourse/instruction to support students' multilingualism and ultimately increase language-learning opportunities among linguistically diverse students.