An in-depth investigation of the inner components of cooperative learning methodologies was made, concentrating on five basic research questions. These were: (1) Do teacher's focusing questions and interaction with students during cooperative learning facilitate students' critical thinking skills? (2) In what ways do cooperative learning groups affect students' leadership roles and communication patterns? (3) What is the nature of student-to-student interaction during individual task assignments? (4) In what ways do cooperative learning skills affect subsequent work behaviors during non-cooperative learning time? (5) In what ways does a cooperative learning environment affect students' behavior? Subjects were a class of fifth-grade public school students who were placed into heterogeneous cooperative learning groups based on the variables of student leadership tendencies, academic achievement, and ethnicity. Four social studies learning modules that used the Group Investigation model of cooperative learning were implemented. This methodology and subject area were chosen on the basis of the class's previous successful experiences with this model in the social studies area. Follow-up research was conducted the following year when the subjects were in the sixth grade. Data were collected through videotaping, student profiles of three at-risk children, students' journals, a student work preference questionnaire, and matrices on leadership, communication, and student work behavior. Findings are discussed and recommendations are offered. Citations number 39. (RH)