This article is a study of "Mosaic"--a piece of multilingual theatre-in-education designed to promote linguistically diverse practices in primary schools in Birmingham, United Kingdom. Focusing on the relatively uncharted territory of applied theatre as a means of promoting multilingualism, and challenging a culture of monolingual teaching and learning, the article examines how the piece enabled schools to begin to be re-imagined as places where creative, multilingual pedagogy and practice could take root. Two key theoretical concepts frame the study: (1) Postman's view of education as a "counter-argument" to the prevailing biases of dominant cultural practices and (2) Bakhtin's concept of "heteroglossia," which links multilingual practices to their social, political and historical power hierarchies. Based on data collected during the touring of "Mosaic"--primarily audio recordings made of the interactions of six participating pupils--the article explores how the participatory approach adopted in "Mosaic" sowed the seeds of "counter-argument" not only to challenge dominant monolingual norms but also to enable children to negotiate and perform new social identities in relation to their multilingual resources. Implications for practice and future research are also discussed.