I'm reading Alicia Juarrero's book Dynamics in action: intentional behavior as a complex system. One point she makes is that of "enabling constraints." Take the example of language in which rules, or constraints, on how sounds can be put together, enable meaning to be communicated. Without rules, language would be only noise. This perspective on learning is a good counterbalance to the prescriptive vs. "anything goes" dichotomy presented in pedagogy. The difficulty in a classroom activity, I imagine, would be determining ahead of time, what sorts of constraints would enable rather than disable.