A Brief Word About Student-Centered Classrooms and Self-Learning

This may not be at all what Zeinab had in mind when she sent in a question about self-learning and student centered classrooms, but it is what popped into my head (sorry, haven't got much sleep this week, you all are testing my "strength" these days :)
When I look at the scope of my curriculum, I always identify what I consider to be five or six of the most important concepts that I will continue to build upon (not always the same the book or the curriculum guideline identifies). From there, I drill down in two ways: 1) As I mentioned in an earlier post about elicitation, I work hard to find a few very concrete, experiential activities to start the foundation of the concept in my class, and 2) I want to find an extrapolative range of activities for the concepts - in other words, I will determine what the minimum set of concepts are that I want all students to get, but then also some more advanced, "extra" levels some students might be able to explore.  I do this because of my commitment to group work and the more capable peer philosophy.
I want to have the students work together to help each other form and solidify concepts, but I don't want to foster a "regression to the mean" (sorry, I have been itching to use that term for a month now, don't know why) where we end up teaching to the middle, losing the more advanced aspects of the concepts and the interest of the our more capable students.  I work hard to get the students and their parents to accept this team philosophy in my class, so I need to guard against a few typical pitfalls (I hope you notice I throw in as many idioms as I possibly can :).
If I am doing a unit on irregular verbs, I determine the most common that I want all my students (or at least most of them) to know.  I then have them work together on finding them, conjugating them, spelling them, etc.  I will pair them in teams using the MCP formula, but I will not keep them together for the entire lesson.  I will let the MCP work with the other student initially, then give her (and maybe some of her fellow MCPs) a second, more advanced task to work on.  This second task will have a tough time restriction (time being the second level of challenge for these precocious students, difficulty the first), and I will make sure they return to their original pairs to finish up the first task before the activity ends.  I can also extend these advanced tasks into homework or other projects.  The point here is that the MCP is rewarded for working with her peer, not punished because she is more capable. 
I like these "extended topics" places where I can let some students go beyond the minimal concepts - and many times, I find that it isn't always the same MCPs who get to do this. If I do my job right, I will find different interest levels that will spark many of the students in the class to occasionally go above and beyond.  The really neat thing here is that once a students accepts the challenge to stretch the topic, I don't have to worry about all the pounding and reviewing I have to do on the simpler levels!
*A note about parents accepting the MCP concept: When I taught younger students, or when I trained teachers who worked with younger students, we often had complaints from the parents of the MCPs that we were holding their kids back by making them work with "slower" students.  On more than a few occasions, my response has been this: "I understand your concern, and I agree that your child is very gifted, and I want to see him reach his full potential.  As you may know, I offer Mahmoud a few advanced projects that allow him to go further than the other students, but I am doing something else for your child - Mahmoud is very bright, and he will be a leader one day I am sure of it!  And when he gets out there in the world leading others, he will need to know how to communicate with those he will lead and how to guide them.  By helping me from time to time in the classroom with the other students, we are preparing Mahmoud for this very promising future......"  I say this with a straight-face because I truly believe it.  I also know and believe that Mahmoud has things to LEARN from the other students as well!