With U.S. classrooms increasingly characterized by linguistic diversity, policies mandating teacher training around English learning have proliferated. Recent federal oversight prompted Massachusetts to implement an initiative to endorse its 70,000+ teachers in Sheltered English Immersion (SEI). While policy research has productively emphasized teachers as policy interpreters within such initiatives, almost no research exists on the role teacher educators play in the policy interpretive process. Therefore, this study documents how teacher educators across Massachusetts interpreted and operationalized the SEI endorsement policy. Drawing on document and interview analysis, findings highlight key experiences, contextual factors, and ideological dispositions that informed participants' policy interpretations. Instructors navigated tensions between their own goals to affirm linguistic diversity and the monolingual orientations produced through the state's recently overturned English-only policy. These findings demonstrate the affordances of examining the role of language ideologies in policy interpretation, with implications for large-scale language policy initiatives and educational policy interpretation more broadly.