Collaborative peer learning environments have received increasing attention in classrooms due to the potential for improving learning and achievement. Yet previous research shows that not all students benefit from the collaborative experience. This paper explores the nature of helping behavior within peer-directed small groups that may be most effective for learning, especially for students who have difficulty with the material. Drawing on examples from recent research on student learning in collaborative mathematics classrooms in a US middle school, we identify student behaviors that are necessary for effective help seeking and help giving, as well as responsibilities of teachers in establishing classroom conditions that bring about effective helping behavior. The findings show that effective help seekers ask precise questions, persist in seeking help, and apply the explanations received; effective help givers provide detailed explanations of the material as well as opportunities for help recipients to apply the help received, and monitor student understanding. These critical helping behaviors reflect the constructivist views embodied in Piagetian and Vygotskian perspectives on learning in social contexts.