There's a couple of problems with having the experienced kids teaching the beginners. One is that while you may assume that the experience kids have the knowledge, there is no guarantee they do. Two, as a whole, they are not trained to be patient, teach sequentially, and dispense technique. Thirdly, they might resent the fact that they must take their time (which they wanted to use to actually advanced their own work) to teach others.
My suggestion to Joe in a nutshell was set assignments (and post them with distinct deadlines) for the advanced students that are truly "advanced", and have them use him as a facilitator, and then work with and teach the beginners what they need to know and pair them up for support, use of clay/tools. Set their assignments to meet what you are teaching (clay techniques, glazing techniques, use of materials, etc) the beginners.
> First thought, off the top of my head: have the experienced ceramics students
> teach the beginners.