This qualitative study examines how secondary teachers (6th-12th grade) navigated tensions of knowledge and practice while supporting culturally and linguistically diverse (CLD) students in a district with a history of not meeting federal requirements for serving English learners (ELs). Through the U.S. Department of Education's National Professional Development grant program, the teachers completed a master's degree in Educational Equity and Cultural Diversity and a Culturally and Linguistically Diverse Education (CLDE) endorsement. We use a critical sociocultural perspective to explore teachers' appropriation of knowledge during the first semester-long graduate course as they grappled with new frameworks of multilingualism and advocacy rather than monolingualism and compliance. Findings illustrate how secondary teachers negotiate tensions that arise as they navigate conflicting district demands for student language and literacy development alongside emergent visions for more culturally and linguistically responsive instruction.