Among inequities faced by multilingual learners, engagement in science education is one of the most persistent. Research suggests leveraging students' full multilingual repertoires in science education can help address this gap. However, pervasive monolingual norms in schooling may impede multilingual engagement, impacting students' multilingual identities and self-perceptions as science learners. Using observations and classroom artifacts from four seventh-grade life science classes in a linguistically diverse school district in the Southeastern United States, we documented one teacher's attempts to engage students' multilingual repertoires in science education during a four-week instructional unit. Our findings indicated student hesitancy to participate multilingually in science discourse. Using critical language awareness (CLA) as a lens, we draw connections between this reluctance and monolingual schooling norms that impact students' multilingual identities and present challenges to implementing linguistically sustaining pedagogies in English-medium instructional environments. By focusing on engaging students' multilingual repertoires in science education, these findings have the potential to advance research on teacher CLA--including its affordances and contextual limitations--in science education and beyond.