Purpose: This paper aims to examine two teachers' beliefs and practices on teaching writing at an urban, high-performing middle school to determine: What discourses of writing are being taught in an urban, high-performing US public middle school? What factors prevent or enable particular discourses? Design/methodology/approach: Drawing on case study methods, this study uses a single-case design with two seventh-grade teachers at a high-performing urban school as embedded units of analysis. Data collection took place over one semester. Data sources included observations and interviews with the two teachers, an interview with an administrator and multiple instructional artifacts, including unit and lesson plans. Observational data were analyzed using a priori code for writing discourses (Ivanic, 2004) and interview data were analyzed for factors affecting instruction using open, axial and selective coding. Findings: Both teachers enacted extended multi-discourse writing instruction integrating skills, creativity, process, genre and social practices discourses supported by their beliefs and experience; colleagues; students' relatively high test scores; and relative curricular freedom. However, there was minimal evidence of a sociopolitical discourse aligned with critical literacy practices. Limits to the sociopolitical discourse included a lack of a social justice orientation, an influx of low-performing students, a focus on raising test scores, data-focused professional development and district pacing guides. Racism is also considered as an underlying structural factor undermining the sociopolitical discourse. Research limitations/implications: Although generalizability is limited because of the small sample size and the unique context of this study, two major implications are the need to layer discourses in writing instruction while centering critical pedagogy and develop teacher beliefs and knowledge. To support these two implications, this study suggests developing university-school partnerships and professional development opportunities that create a community of practice around comprehensive writing instruction. Future research will involve continuing to work with the participants in this study and documenting the effects of providing theory and tools for integrating the sociopolitical discourse into middle school curricula and instruction. Originality/value: This study contributes to the field of literacy education's understanding of internal and external factors limiting the sociopolitical discourse in a high-performing, urban middle school in the USA, an understudied context.