This qualitative case study analyzes how a middle school teacher used the tools of systemic functional linguistics (SFL) and genre based pedagogy (GBP) to support linguistically and culturally diverse students in analyzing informational texts critically in the context of curricular and school reforms in the United States. Using a combination of ethnographic case study methods (Dyson, 1993; Davies, 1999; Merriam, 2005; Dyson & Genishi, 2005) and critical discourse analysis (Eggins, 1999; Fairclough, 1995) the teacher collected an extensive corpus of diverse data over a school year. Focused data collection consistent with case study methods included instructional materials, paper and electronic copies of students’ texts over time, videotapes and transcripts of classroom interactions and transcripts of interviews with the teacher and focal students. Data analysis included tracking the ways students discussed language and genre features of instructed informational texts, as well as using discourse analysis to analyze the specific genre register features included in students’ written products and making revisions to their expository texts. The findings indicate when introduced to an SFL metalanguage, students in this English class were able to discuss the language of school on a more functional level, shifting from their more structural conceptions of texts demonstrated at the beginning of the school year. In addition, students co-constructed a metalanguage for their own needs as writers, naming language systems in ways that made sense to them as developing writers. Finally, the student writers did gain more control in the academic language employed in writing, best understood with the tools of discourse analysis. The implications of this study suggest expansive language resources used to discuss academic literacy act as tools for students in learning to read and write instructional texts.