In many ways, the micro-RPG Spirits in the Night feels like taking only that and seeing where it goes.
Part of the Indie Megamix Mixtape, SiN is about a group of friends meeting one last time around a campfire before all going their own ways. It isn't explicitly about graduating from high school but you'd have to modify the game to make it about something else.
The players create a group of five characters, picking Who (their role in the group), Wish (motivation) and Future (what they plan to do after this last night) from lists. You draw cards from a regular deck of cards to determine relationship strengths between characters, which can be negative.
During the game itself, players take turns choosing a character and having them interact with another character. You play out the scene by playing blackjack
with the end result changing their relationship. Other players can step into to play characters. Jokers mean an outside party has disrupted the campfire. Play through the deck twice and then give everyone an epilogue.
The one mechanical thing I like about Spirits in the Night is that it is a GM-free system that is an ensemble all the way through. Not only does no one own any of the characters, no one ever takes on the role of temporary game master. That doesn't necessarily make it a brilliant design but I do admire how thoroughly it breaks the paradigm of RPGs.
At first, Spirits of the Night didn't interest me as more than an intellectual exercise. Then I realized that it describes the basic origin of the heroes of the lance from the Dragonlance Chronicles.
At that point, I thought that if you adjusted the lists for Who, Wish and Future a little, I can see playing a game of Spirits of the Night to set up a campaign (D&D or otherwise). Play the game, have people choose characters, roll them up, and start the campaign ten years later. Everyone starts off with a shared background and connections.
I'm not interested in playing Spirits of the Night as a standalone game. However, I think it would be a really great tool to set up a D&D campaign.