This case study examines how three science teachers in a secondary school attended to the language demands of science through oral interactions in classes of multilingual students with diverse English proficiencies. It specifically unpacks the intricate role of language in science education, where teachers must address disciplinary-specific language demands as well as build academic language, within a policy environment that stresses English as medium-of-instruction for science education. Thirty-nine video recordings, comprising three full sets of lessons on the topic Human Circulatory System, were analysed. Instances of whole-class discussion during which an aspect of language (e.g. form, meaning or type) was addressed were the focus of analysis. The analysis shows some common features of language support across teachers, especially in terms of teaching scientific terminology, as well as features that provided additional support from one teacher. These features included unpacking the language demands of science beyond discrete terminology and use of students' language. The article highlights interactions which can contribute to student opportunities for meaning-making in science.