The American educational landscape is changing rapidly, and so are the students in American mathematics classrooms. In the New York City public schools, one of every four students is an English language learner (ELL) (New York City Department of Education 2014). Mathematics teachers find themselves teaching either in a classroom that contains all ELLs at different levels of English proficiency or in a mainstream mathematics classroom with a mixture of English speaking students and ELLs. Student diversity enriches teaching and learning but also brings challenges to mathematics teachers, challenges compounded by new learning standards and demanding graduation requirements. This article discusses ways to build a responsive learning community by providing language and culture support and integrating language instruction into mathematics teaching. A bibliography is included.