The group investigation method of cooperative learning (CL), and its contribution to the heterogeneous classroom, is the subject of this article. A wide range of ethnic and cultural diversity among students in the classroom, as occurs in Israel as a nation of recent immigrants, requires a differentiated approach to instruction not provided by the uniformity inherent in traditional whole-class teaching. Group investigation through positive peer interaction in small groups increases students' motivation to learn while providing for flexibility and variety in the content and pace of teaching and learning.