Informal collaborative projects have grown into structured, cooperative group work. Cooperative learning became especially popular in the early 1980s and has matured and evolved since. One evolving aspect of cooperative and collaborative learning is the thinking about the best ways to compose the small groups. Debates still occur on this topic. Researchers disagree mainly about whether to group students according to their ability, or to mix them so that stronger students can help the weaker ones learn and themselves learn from the experience of tutoring.
More researchers support diversity in small groups, however.
With good arguments on both sides, most teachers make choices based on their objectives. Or, they simply alternate. Sometimes they group according to the strengths or interests of students, and other times they mix it up so that students can learn to work with different types of people. Just as experts differ on the make-up of groups, they also debate about the most effective size for small groups. Antil et al.