Students who speak languages other than English are a growing presence in U.S. schools. As a result, many mainstream classroom teachers are finding that they have English language learners in their classes. Unfortunately, most mainstream classroom teachers have had little or no preparation for providing the types of assistance that such learners need to successfully learn academic content and skills through English while developing proficiency in English. In this article, the authors identify a small set of principles that can serve as the linguistic foundation for the teaching of English language learners in mainstream classes. The authors then outline linguistically responsive pedagogical practices that flow directly from those principles. They conclude with concrete suggestions for how teacher education programs can incorporate the knowledge and skills that will prepare all preservice teachers to be linguistically responsive. (Contains 1 table and 2 notes.)