This may sound weird, but I vote for the Ed's from Ed, Edd, & Eddy, Ed for either CoMC (who know more mythology than him) or DADA (Once again, who has more theoretical monster fighting knowledge than him), Double D for Muggle Studies (Help the wizards see the light of modern science and assign homework on sticky notes) or Arithmancy (it's basically magical math class) and Eddy handling broom flight and Quidditch (Don't know where else to put him). Rolf could take the class big Ed doesn't (superstition helps him some) or more likely herbology, Jimmy takes potions (it's kinda like cooking, if only it wasn't in that dreary icky dungeon), Sarah could help him (When is one really without the other), Johnny 2X4 takes Divinnation (He's as batty as Trelawny, and sees the futre with his magic plank), Marie Kanker could be History (She did, at one point, show knowleadge on art history at least), and May Kanker working as the care taker.
No Ideas on Nazz, Kevin or Lee.
I have a serious reason for one, I really think in the show, big Ed is genuinely magical, how else could he regularly bend and/or break laws of man, nature and physics, while keeping a brain the size of a walnut.