With not only a rapidly growing number of international students but also historically underrepresented domestic students who grew up in multilingual households, U.S. higher education has become a more and more linguistically and culturally diverse space. New curricular and instructional challenges have been posed to First-Year Composition (FYC) courses that are widely taken by college students from a variety of linguistic, cultural, socioeconomic, and sociopolitical backgrounds. Second Language Writing (SLW) and Composition Studies unfold for us the complexity of writing as a social process, the inseparability of writing and its social context, and the tension peripheral participants encounter in the process of socializing into unfamiliar discourse communities. Projecting the spotlight on six first-year graduate student teachers of FYC (titled teaching assistants or TAs in the specific institutional context), this study expands upon and deepens our understanding of FYC teachers’ academic discursive practices in relation to their diverse student populations. Working from the premises of teachers as transformative intellectuals (Giroux, 1988) and composition as a cultural practice (France, 1994), and taking a translingual approach towards language differences (Horner, Lu, Royster, & Trimbur, 2011), I tap into FYC TAs’ conceptualizations of and positionalities towards academic discursive practices and diversity, as well as professional and personal resources that helped facilitate their conceptualizations, positionalities, responses, and practices. This close examination unpacks the complexities composition teachers have to navigate in thinking about what academic writing looks like in the particular institutional and their own classroom context, issues around diversity such as identities of students and teachers that are more or less visible, and the absence of power in institutional discursive constructions around diversity. Drawing from the frameworks of Community Cultural Wealth (Yosso, 2005) and Nexus of Multimembership (Canagarajah, 2012; Wenger, 1998), my study proposes important implications for individual teachers and teacher training programs, such as carefully examining assumptions about teaching, the teaching of writing, and teacher training; and more productive use of contact zones across the disciplinary, professional, and personal as a way of facilitating praxis and transformative teaching.