Cooperation and collaboration are natural processes. Such skills are useful when the creative process benefits from interdependence. The best collaboration mirrors democracy when individual talents, knowledge, or experiences are contributed to produce something larger than the sum of its parts.
Work with your friends. Work with people you trust. Work with people who have different skills or expertise. If that doesn’t produce the result you desire, you will find others to collaborate with. That is how you learn to collaborate. You may teach it, but the students will not stay taught.
Honestly, I could not care less about whom my students (kids or adults) choose to work with. The only reason to assign group size is scarcity of materials (we have to share). Even in those largely avoidable scenarios, it hardly matters if group size varies a bit. The main consideration is inactivity by some members when a group is too large.
Collaboration is both selfish and selfless. You give of yourself by sharing your talent and expertise, but the collaboration should benefit you as well.Source
This is a useful provocation in thinking about technology and 21st century learning.