Except that the geography is not perfectly orderly, their teachers are not in complete control, and it might be interesting to bring back an earlier set -- the characters in the first appearance were raucous but not fundamentally dangerous, and in the second would, well, be fundamentally dangerous (as well as raucous).
Or possibly one of the other sets could fill the same role. Especially since one topic of conversation has been how sloppy their classification is, being purely pragmatic, and by the most prominent trait among those with several. (Mostly having to do with what offer would be the most plausible, allowing them to be tricked.)
Such is the issue of structuring something that doesn't work directly from cause and effect.