This publication aims to help teachers to more effectively teach math and science to English language learners (ELLs). It argues that the learner's home language can play an important role in his or her science and math learning, whether or not the teacher speaks that language. When students are allowed to use their home language in the classroom, their academic performance improves, which can help them to build a solid foundation in math and science concepts before entering the higher grades where language becomes more decontextualized and cognitively more demanding. Skills in content areas like math and science, once learned in the first language, are retained when instruction shifts to the second language. The book is divided into several sections including the following:"Understanding the Specialized Languages of Mathematics and Science"; "Linking Second Language Strategies with Content Instruction"; "Thematic Instruction"; Cooperative Learning"; "Inquiry and Problem Solving"; "Vocabulary Development"; "Classroom discourse"; "Affective influences"; "Assessment"; "Collaborating with Other Teachers"; and "Involving the Family." There are also three "scenes for the classroom," where practicing teachers share what has worked well for them in their classrooms. (Contains 58 published references and 4 general organizational references.) (KFT)