I've had strong success in the last few years framing campaigns within school settings. That background provides rich opportunities for role playing, solves some campaign start problems and supplies an easily grasped structure for both the players and the GM. Obviously right now the grand-daddy of that form in literature is the Harry Potter series. But other books, Patrick Rothfuss' The Name of the Wind, Mary Gentle's Rats and Gargoyles, Sherri Tepper's True Game, and John Wright's Orphans of Chaos all use that for different purposes. It pops up heavily in Japanese narratives, both manga (Fruits Basket, Bleach, and Naruto) and anime (Evangelion, Shikabane Hime, Ikki Tousen). Likewise it appears in a number if jrpg video games (the Persona series, Mana Khemenia, and Final Fantasy VIII). In American lit we can see it in comics (the X-Men, Gunnerkrieg Court), television (Buffy, Veronica Mars, Galaxy High), and movies (The Faculty, Sky High). For some fringe cases you can even point to Volcano High and Battle Royale.
A number of rpgs have also built games or published supplements revolving around these kinds of themes. Teenagers from Outer Space and Curriculum of Conspiracy use pre-college settings. The d20 supplement Redhurst Academy of Magic tries to shoehorn a very HP-like structure into the multiverse of existing D&D settings, with mixed success. Miskatonic University could easily serve as a starting place for a Call of Cthulhu campaign, though the question would be how long the campaign would remain there before moving away (or having the rampant strangeness overwhelm the grounds). For high weirdness, there's GURPS IOU. In the supers genre, M&M has a sourcebook, Hero High, devoted to these kinds of games.
Below are some thoughts drawn from my experience running four campaigns with a school focus (either in the foreground or background) and having played in one.
One of the most obvious benefits of a school setting is that it provides a rich pool of NPCs of very different kinds. If the school draws on an international (or larger) pool, the GM has the opportunity to showcase a number of different cultures. One trap the Gm should be careful of is overdoing it, however. Select a few notable classmates, rivals, a couple of notable upperclassmen, important administrators, staff and the teachers for the PCs subjects. Even that will, depending on the setting turn out to be a pretty big list. GMs may find it really useful to hunt down pictures if possible to add to the flavor. Since these characters will be consistently recurring, it means that effort won't be wasted. PCs will have to interact and develop at least some kind of relation with these NPCs so taking the time to flesh them out pays off.
These kinds of campaigns also encourage a different kind of approach from simple brute force. Players shouldn't want to get kicked out of the school-- so they have to find other methods to deal with their rivals, even those in charge. A school setting gives real focus to characters with social and sneaky talents. Rumor mongering, pranks, building reputation, succeeding in academic contests-- the players can best their rivals on different levels and in different ways. There's still room for more direct conflict, but it must be managed carefully or off school grounds.
Robin Laws in HeroQuest 2e makes an interesting point about character development. Experience points and continuing growth are really an artifact of classic role-playing systems. Generally in most conventional dramatic narratives we see characters at a certain skill level throughout. They might pick up a few tricks, but those aren't core to the story. The exception to this is the school/educational based story setting, in which the growth of the character in skills parallels personal development. In other words, putting characters in a school can explain why they start out sucky and get better. It explains how characters can amazingly develop many new skills, abilities, feats and the like without mechanics for side-quest training time or having them miraculously appear.
But mechanics aside, the school setting allows characters to grow into who they are. Often when players make up characters, they've already established some of the major events of those lives. They know their purpose, profession and ideals generally. A school gives players the space to figure those things out based on the events in front of them, with less baggage to shape those decisions. In point based games like GURPS players can begin with disadvantages, here they can actually pick those problems up. Significant first moments can be played out, since the players are still relatively young. In our fantasy steampunk HP-esque campaign, Libri Vidicos, the first time a couple of the players had to kill other people, when attacked on a field trip, they had to deal with their reactions to that. It made for some really nice moments at the table.
The school setting really allows players to buy-into the setting. One the one hand players will likely be familiar with the dramatic conventions from all of the narratives mentioned above. They know that students have restrictions and make their fun within the limits of those. On the other hand, most players will have been in a school for a good portion of their lives. That's an experience they share with their character, where other aspects of the character's life may be foreign to them. Players know how schools operate-- with good and bad teachers, the pressure of homework and the potentially awful web of social interactions. These two level of empathy allow a player to riff and improvise easily within the setting. They can fill in the gaps in the imaginative space presented.
Players often begin with a deep suspicion of authority and value autonomy over their choices. That's not necessarily something to be stifled. The problem lies where players instinctively react negatively to anyone who seems to be giving them orders. The school setting shifts that a little-- there's a built in give and take between players and the authority of the school (administration or teachers). The players have to find other ways to get around those authorities, since those groups are providing something they want (training, shelter, and so on). The player needs to be creative in their responses, resorting to hijinks and mischief to get around the authority. As well, punishments for defying authority aren't final: detention, bad marks, being kept from activities and so on. There's a give and take there.
Structures of the School
In Harry Potter you know classroom scenes will probably do at least one of three things: illustrate character interactions/development, provide a goofy humor moment, or foreshadow an important plot point for later. I enjoy using the last of these things fairly liberally in the campaigns. It works best in classes which the various PCs share, but can be done for one or two PCs in a class at once. Throughout the campaign I'll throw in lectures from the classes, probably no more than one or two per session and no more than one or two from any particular class. That reminds characters they are in a school and keeps the flavor of what's happening without it being overwhelming. In those lectures, especially early on, I'll bury points that will come back later. It can also be used to establish things like moral or ethical choices which appear later- creating a contrast between talking about something and actually having to do it.
Lectures serve another important purpose. They allow the players to learn about the world as their characters do. Players often begin a game with a blank map of the game world, unless they've played in or read about that setting before. A GM who has built an extensive background and history for their world often finds it hard to get some of those ideas out into play. This ought to serve the path of the story-- a GM should be careful about info dumping. While the tale the GM's woven in their head is undoubtedly rich and interesting, focus should be placed on the details which will come back later. Otherwise there's a risk of having players tune out if they think the material is just exposition without purpose.
Besides classes, a school game gives the GM an interesting variety of set piece events. Clubs, field trips, performances, athletic contests, inter-house competitions, guest lectures, dances, hall parties, detention, tracking down mentors, researching topics in the library can all be used in the game. If you're campaign goes on long enough, players will be begin to anticipate and prepare for these. For example in Libri Vidicos, as first year students, the characters didn't get to go to the big dance. Instead they had to serve as staff for it. That made it all the more interesting the next year when they were able to go. These events can also reflect changes in the administration's character. In Year Three of LV the new Headmaster has restricted students to only being a member of a single club, forcing the PCs to choose only one of their groups and establishing a certain amount of tension.
A secondary benefit of the school campaign is that it provides a “home base” from the start for the campaign. Generally in the games I've run players live at the school itself, providing an insular setting. Players return to the school and their rooms for some safety and regrouping with privacy, after a caper, after a field trip or even after a long vacation. This answers one of the basic needs of a group: shelter and security so that they can focus on other needs. As well, the GM can contrast this safety later: having to forge for themselves while they're “in the field” or if something bad happens in the school making their position unsure.
The structure of the school year provides a nice form for the players. You have pretty clear markers about the progress of he story, some clear stopping points for sidebar adventures, and some room to time lapse forward. As a GM, don't feel bad about saying something like “...but the pressures of class and work meant that they weren't able to look into that matter for another week.” Special events like sports can be also used to mark time. On a higher level, the breaking up of the campaign itself into “years” which serve as books allows players to make some mental changes and have a sense of how far the larger campaign has progressed. In the case of Libri Vidicos, I told them right from the beginning the campaign as a whole would cover five school years. We got through year one in a year real-time, and year two in a year and a half. I think that reflects some of the bloat Rowling had in her own series. Ideally I would like to get through each school year in one year or so of play.
While the school setting can easily be used for lighter games with perhaps a touch of campiness ala anime, they don't have to be used that way. Consider the training camps of Starship Troopers or Full Metal Jacket. There can be a singularly awful aspect to the school as well, forcing students to try to survive within that place. These kinds of settings can also be used just as a starting point for a campaign, a period of development contrasted to action or escape later on. If the school's a bad place, players may find their way out and then have to evade capture and figure out how to defeat their alma mater later. The destruction of a school while the students are there could provide a great and shocking framework for a campaign with a strong dramatic shift in the middle.
Changes in administration or scholarly focus can be used to change up the setting if players get too complacent. PC actions may cause some characters to die, retire or be fired. That can shift the hidden balance of power as to the school's agenda resulting in changes the PCs didn't expect. If a campaign extends over a couple of years, each one should have a dramatic theme or difference the group can identity.
Levels of mysteries can presented within the school itself, but the game doesn't have to exclusively focus on that. Field trips, missions, holiday recess, visits home and so on can be used to break up the action. Done sparingly these kinds of moments help reinforce what makes the school setting different. Home visits (or even visits to the school by parents) allow the characters to reflect on what has happened. GMs may want to allow PCs to visit each others' homes or homelands to help show what made the PC who they are. In one case, a particularly awful rival NPC gained immediate sympathy from the PC group once they met his mother. Suddenly they could see why he was that way and they made an effort to break him out of those behaviors.
Keep in mind that in using a school setting, it doesn't have to overwhelm the game. GMs can try out material and judge how central those issues should be-- based on what the players seem to be enjoying. For our Libri Vidicos campaign, the school is front and center, shaping the play. While there are plots and stories happening outside the school, they all eventually intersect with the school itself. As I said before, while is is a fantasy steampunk game, it draws on HP pretty heavily and that's what the players enjoy. On the other hand, for my Changeling: the Lost campaign, while the characters are at a school, that isn't the centerpoint of the game. Instead it is a place of refuge and a location where they can interact with a few normal people of their age. So in this case I don't play out the classes so much or have big events, instead I make occasionally reference to how the school sometimes impacts their out of game lives. The game may also have an even more dramatic split, as in the "Neon Genesis Zombi"e game I ran (An AFMBE game based on Evangelion) in which we had an absolute split between their school lives and their mecha piloting secret activities. Finally, as I mentioned before, the school can simply serve as a starting or jumping off point, a prologue or first part of the campaign, establishing the group together for the big dramatic shift.
GM Prep Needed: Basic layout of the school; list of classes; list of rules; NPCs same year friends, same year rivals, select upperclassmen, teachers (for the classes the PCs take), staff (nurse, cook, security, etc), administration (headmaster, house master); and a few events.
The School Campaign: Examples from Libri Vidicos I
The School Campaign: Examples from Libri Vidicos II
The School Campaign: Examples from Libri Vidicos III
The School Campaign: Examples from Libri Vidicos IV