On entering Mr. Wilson's seventh-grade classroom, the authors immediately noticed the students talking about mathematics and their teacher listening to them. To create an interactive learning environment that would stimulate and perpetuate discourse, Wilson discussed two main issues with his students: (1) What the students and teacher would do in small groups; and (2) The roles of both students and teacher during whole-class discussion. In small-group work, students were asked to consider taking on interactive roles. They were organized into pairs and expected to work together by assisting with the problem, listening intently, sharing their ideas, and explaining their problem-solving strategies. The focus during the whole-class discussion phase was on having students explain how they found their answers and how they reasoned--not just the answers themselves. The intricacies of the Greek Cross activity supported problem solving, interaction, and communication. Wilson chose the task because it required students to use tools to create models, to analyze the figures at various stages in the growth cycle, and to find patterns. These models, or representations, were intriguing and colorful shapes that stimulated interaction and generated discourse in both small groups and in whole-class discussion. (Contains 6 figures.)