Developing academic writers must continually position themselves discursively as they negotiate institutional, programmatic, and disciplinary contexts. The inextricable relationship of writing and identities raises questions of access to social identities in schools, a particularly salient issue when considering the complexities and challenges of the high school to college transition for students from historically marginalized groups. This study focuses on Jain, a first-generation Latino college student, as he positions himself as a writer over 18 months in response to a range of school-based writing tasks. My analysis finds that Jain's identity negotiations are influenced by a history of social positioning in schools, as his stance-making patterns and sense of self as a writer reflect resources and opportunities he encounters. This study adds to research demonstrating the role teachers and institutions can play in (in)validating certain aspects of students' identities and influencing belonging in school spaces, indicating a need for educators and researchers across K-12 and college contexts to continue to challenge the standardization of school writing and the prevalence of assessments that limit curricula and constrain identities.