My purpose for writing this book is to discuss what constitutes effective instruction for students for whom English is not their native language. As an English as a second language educator who prepares prospective teachers for their work with a diverse student body, including non-native English speaking students, I hope this book will provide one point of departure for bridging the gulf between subjects and provoke conversations among all teachers as they reflect on their practice as their classrooms become more linguistically and culturally diverse. This book is intended for high school content teachers, preservice teachers who prepare to teach in a subject matter area, college faculty involved in both pre-service and in-service teacher preparation programs, curriculum developers, and policy makers in teacher education. In this book they will find teaching principles as well as concrete ideas for teaching content subject matter knowledge to diverse students. Taken science, social studies, English, and math as a content example, many ideas and strategies described in the book can be applied to other content area teaching also.