Yes, good point about different levels of competence and confidence in the given subject matter
Perhaps classifying students/classes according to something like the Dreyfus & Dreyfus (1980) model of different levels of expertise, from novice to expert, would be helpful in some cases. Although that model is aimed at learning technical, practical, directly observable skills, it's been successfully adapted and applied to cognitive skills too, e.g. Patricia Benner's work on nursing practitioners (2004).
And I guess another significant factor is the personalities and expectations of particular cohorts/groups of students. It may take some preparation to cultivate a climate and set expectations that are more appropriate to the desired levels of collaboration and responsibility.
What do you think?
P.S. Only adding references so that anyone who wants to look into it further can do so easily. Don't want academic stuff like this to get in the way of open, frank, and spontaneous discussion