Despite the fact that no one knows exactly how or why collaborative learning works, many learning situations that center around peer group activities have shown impressive results.1 Well-known success stories about uses of collaborative learning methods to promote cognitive and metacognitive skills in various academic subjects include Lampert's (1986) sense-making approach to teaching multidigit multiplication; Palincsar and Brown's (1984) reciprocal teaching method to impart reading comprehension strategies; O'Donnell et al.'s (1988, 1990) scripted cooperation, a variation of reciprocal teaching, also designed to improve reading comprehension and to help students learn technical procedures; Schoenfeld's (1983, 1985) use of group problem solving, with the teacher playing the role of “consultant,” to teach heuristics and “control strategies” for solving mathematics problems; and Scardamalia et al.’s (1989) techniques of procedural facilitation via prompts or “cues” to develop students’ control over the writing process.2 In each case, students assume some of the responsibility for their own and other students' learning, by working together on tasks that give them practice in using the concepts, learning strategies, and problem-solving procedures they will-it is hoped-eventually internalize.