This chapter examines the themes of agency and policy with specific reference to increasing linguistic diversity in Australian secondary schools, and examines (a) how monolingual and monolithic English-only language ideologies impact upon schooling practice, and (b) the extent to which increasingly linguistically diverse teacher and student populations exercise agentive responses to these. The author examines policy conditions that lead to incongruities between the rich language resources multilingual teachers and students bring to the classroom versus the enactment of a monolingual ‘English-only’ habitus reflected in language-in-education policy in Australia. Drawing upon data from a qualitative, ethnographically oriented case study research project conducted with teachers, pre-service teachers and students at an intensive English secondary school catering to multilingual students from migrant backgrounds, this chapter discusses how teachers understand and enact translanguaging pedagogy within the constraints of an intensive English immersion program. Surfacing throughout the chapter is a conceptualization of teacher interactions with students as ‘contact zones’, where languages and cultures come together, often in contexts of conflict and misunderstanding, within social spaces characterized by unequal power relationships. From this conceptualization, the author advocates translanguaging teaching practices that enable students to draw upon their existing funds of knowledge, thereby affirming their cultural and linguistic identities and in turn enabling them to respond authentically and agentively to learning opportunities in the classroom. The author concludes by contending that the enactment of translanguaging teaching strategies in classrooms, where students and teachers hold diverse resources across multiple languages, is a valid—albeit often contested—agentive response to English-dominant language policy in Australia.