Mutants and Masterminds would probably work decently, with my usual change of the equipment system (just putting fucking money in).
Step One-- Name the PCs Band
Step Two-- Write up a Six Member Band
- The Bravo Courageous, or maybe just foolhardy, to a fault. Gets people to follow him even when he doesn't want it. If he's disgraced, pluck and the help of his Band show people what really happened (or why it wasn't actually disgraceful). Really good at a few specific tricks/spell, but leading and motivating is his shtick. Leo
- The Lancelot(or pick an area appropriate equivalent) Just as brave/foolhardy as the Bravo, just doesn't realize it. May leave the bravo over a disagreement, but never actually betrays him. Inherently capable in a specific area, usually physical, though don't be too surprised if he turns out to be really good at something mental that's related to his interests, like a sporty guy understanding the game and strategy aspects of Wizard's Chess. Irving
- The Mind Smart. Expect them to have all the real knowledge, the trivia, and the most technical skill at magic. Arts, more talent related topics, may give them difficulty, so don't expect them to be seers, but they know more spells and how to execute them flawlessly than pretty much anyone else. A generalist and info dump, with high Magic stat and lots of points in knowledges, low Attack and Defense stats, and a lot of different utility spells. Ran
- The Body[/b] He was captain of the quidditch team in school, put away the most food at his table at dinner, and spent time not taken by classes and practice by running around and exercising. Alternatively, he's just stocky and resilient. Not necessarily dumb, or bad at magic, but the first thing you think when you look at him is "body." Typically the person you can count on when a challenge is more physical than mental or magical. Kratos
- The Sneak You know that guy who, when you're trying to figure out how to get something done, suggests the amoral solution that makes everyone just turn and stare? Yeah, that's this guy. He was probably a Slitherin back in school, and certainly knows a lot of underhanded tricks, like putting out the lights remotely, hiding their presence, where the secret passages are, or how to take out an obstructive friend non-fatally with a sneak attack. Morgan
- The Trickster Makes everyone laugh, until they turn one of their usually harmless but incapacitating jinxes on them. As they get older, they start developing hexes and jinxes capable of harm for when they're needed. Typically they're your boon companion, just don't piss them off. Stanchik
Step Three-- Write up a Three Member Band
Team 1: Leo leads and deals with social challenges, even if only as a distraction. Irving backs him up and lays a bit of smack down when needed. Ran researches and does the mental and magical heavy lifting.
Team 2:[/i] Morgan actually is a Slytherin, and a rich one at that, and so gets through doors by chuckling galleons at people, and makes social situations go away with name dropping, social intimidation, and promised or called in favours. Kratos runs circles around people and dangles them upside down when Morgan being nice doesn't cut it and Stanchik knows what bears are like and so can fool them, and has seen this kind of fire breathing chicken demon before.
Step Four-- Outline an Adventure A monstrous beast has gotten loose in the school. People have been turning up with burns, broken bones from fallen masonry, and mangled limbs. Against all reason, Leo and Irving rush out to combat the beasty, leaving Ran with no real choice but to follow the idiots. Or she got taken out by the thing in the library. But she knows what it looks like, and so is researching it now that she's conscious again. They find out it's a dragon, a young one, but still dangerous, and get it out into the forest where at least it can't hurt any other students. Leo happens to have some artifacts because people like him like that, and they're useful. Irving can run around the thing and back up Leo until Ran runs up and tells them it's weak against (whatever).
(yes, this is a shit adventure, I'm just trying to get *something* here)