The authors explore the theoretical and pedagogical premises of their critical systemic functional linguistics approach, which they developed to challenge the deficit positioning of bilingual students in the Southeast of the United States. As multilingual educators from postcolonial Ireland and India, the theoretical framework has helped the authors conceptualize and design interventions that support the incorporation of the linguistic and cultural repertoires of students while acknowledging that disciplinary literacy needs an explicit form of linguistic instruction. Key tenets of this approach include fostering a third space where voices, languages, and registers of students and teachers interweave to make and challenge disciplinary knowledge domains. The authors' pedagogical and professional work, which they illustrate through discussion of data from a larger ethnographic study, has encouraged their students to switch among registers and languages while appropriating academic discourses in a high-stakes testing culture. It has also supported bilingual students in challenging normative discourses about immigration and other issues related to social inequity.