The number of English language learners (ELLs) in the United States has increased dramatically. Given this increase it is vital for teacher education programs at the pre-service level and professional learning programs at eh in-service level to address the needs of ELLs. This article presents a teacher preparation model--"a language-based approach to content instruction" (LACI)--developed over the past 10 years of research in content area classrooms with ELLs and based on scholarship on the language demands of schooling. LACI building on six principles--connection, culture, code-breaking, community and collaboration, challenge, and classroom interactions--that have identified specific elements of instructional activities for culturally and linguistically diverse students. Drawing on cases of two elementary mainstream content are teachers, the article shows how this approach can be applied in mainstream content area classrooms with ELLs.