In this study, we explore language--specifically the use of Spanish, in a sixth-grade science classroom, where the district recognises English as the official language of instruction. The question guiding our analysis is: How is Spanish positioned in Ms. Cook's science class? Transcribed interaction from twelve weeks of videotaping is coded and analysed to highlight when and how Spanish is used during everyday classroom activities. Most of the formal, public talk during Ms. Cook's science class was in English. Ms. Cook consistently spoke English in discussions, modeling English "science talk". However, during small group work, a significant portion of science class, language flowed between English and Spanish. As students tried to interpret and make sense of science concepts, students chose the language that was most useful to them. In this article, we will share transcript excerpts that illustrate interaction where Spanish and English are both positioned as legitimate tools for students to use when exploring science concepts. The excerpts also show how Spanish was respected as Ms. Cook legitimised Spanish, without translating it or marking it as unacceptable. In this classroom, Spanish works as a significant resource, helping students achieve success in science class.