When you make a show about kids in high school, you are making a show about people who are almost always more clever, brave, and resourceful than any adult, but who are surrounded by authority that limits them, ostensibly in their best interest: teachers, parents, prurient laws and condescension. You are making a show about the struggle against that authority. You are making a show about the agency of disenfranchised people.
And that’s why it’s so hard, and maybe impossible, to make the leap to college–the conflict is gone. Despite some nice moments, Veronica Mars hasn’t handled it well, and my understanding is that Buffy couldn’t either. Let’s not get into Dawson’s Creek. Even Six Feet Under had to keep Claire off campus except for (apparently) one class. And this is the same logic that started killing Scrubs: once JD, Turk and Elliot became residents and gained some authority of their own, the show began drifting from drama-with-jokes-in toward straight comedy.
I’m afraid for the last Harry Potter book, if he really doesn’t go back to Hogwarts.