As elementary teachers in U.S. public schools strive to adapt their instruction to support growing numbers of students learning English as an additional language, they must also navigate institutional constraints and affordances beyond their classroom-level interactions. Even as teachers plan and implement instruction within their own classrooms, their work is strongly influenced by the functional systems at the school and district levels. Despite this growing awareness, few studies have examined how these functional systems impact elementary teachers' efforts to redesign and refine their instruction for multilingual students, often labeled as English language learners (ELLs). Through the use of qualitative methods, this article illuminates elementary teachers' perspectives on the functional systems that afford and constrain their abilities to improve their instruction to support ELLs. As teacher educators of a graduate-level ELL endorsement program for in-service elementary teachers, we sought to investigate what impacts teachers' instruction on a daily basis. This article centers on this research question: How do elementary teachers perceive and navigate functional systems within schools as they endeavor to support multilingual students?