X-Men
Given their 'x-tremely' amusing name by the students of the school, the so-called X-Men were put together by a Charles Xavier who'd noticed his old friend Erik Lensherr and his followers growing increasingly more belligerent, and who'd noticed a glaring hole in his government's ability to deal with mutant threats.
The original team of X-Men was made of the first students of Xavier's School and consisted of Scott Summers ('Cyclops') as leader, and Dr. Jean Grey ('Phoenix'), Ororo Monroe ('Storm'), Dr. Hank McCoy ('Beast'), and Warren Worthington III ('Angel') as his team members. Others have drifted on and off the team roster, such as Logan ('Wolverine'), less recruited and more dragged along for the ride during the events of Liberty Island. All are members of the teaching staff of the school when they're not off saving the world,
The second wave of students through Xavier's has also had some of its numbers called to the team -- a very rare occurrence, further limited by ample opportunities and encouragement to experience life outside the 'Xavier Bubble'. However, Kitty Pryde ('Shadowcat'); Jubilation Lee ('Jubilee'); Bobby Drake ('Iceman'), Wesley Flynn ('Flood'); and Marie D'Ancanto ('Rogue') have made their way through training and now stand as full members of the X-Men.
Inside of the school, the students usually figure out about the X-Men fairly quickly -- they did, after all, give them their name. While incoming students aren't exactly shown the Blackbird hangar as part of the main tour, they're usually filled in fairly quickly by their peers, and directed to the teachers for a proper explanation. They're also given a healthy education in the importance of being discreet.
Outside of the school, the team is known to certain very high levels of the FBI, CIA, and other acronyms as well as a few tenacious NYPD hounds. Aside from the law-enforcement groups, the Brotherhood quite obviously knows of their existence, as does Emma Frost and the Hellfire Club. The Friends of Humanity? They know just enough to be really, really pissed off.
The average Joe on the street? Well, that's what the tabloid news is for.
While Scott is team leader, and therefore in charge of keeping track of who's where, what missions are approved, etc., it's a very rare situation that sees the X-Men all go out en masse to save the day. It's much more likely to see members of the team drawn up and partnered together based on the skills the situation requires.
While the X-Men are all trained in the combat use of their powers, they prefer to avoid open combat as much as possible. There's a fair amount of hit-and-fade rescue, espionage, and simple observation of a situation, and less open street violence. The majority of the X-Men's training is done in the Danger Room, a chamber that, thanks to Forge, is inching nearer Star Trek holodeck capabilities.
There are actually two ways to become a member of the team, and one is much easier than the other. Both depend OOCly on the person interested being someone being sane and mature; a good, stable gamer who can have fun win or lose; who knows the setting well and plays it; and isn't going to take their character being an X-Man as a key point of personal validation.
The first way is as a faculty member or an adult ally of the school. Someone who's an adult, who's known and trusted by the team, has a sensible head on their shoulders, control of their powers, and useful other skills (not necessarily mutation or combat-based) to bring to the table. The X-Men are a secret organization and have ties to the government, so they are extremely difficult to get into, but it is not unheard of for faculty members to be asked to do special tasks for the X-Men, without actually becoming part of the group.
The second way is as a student. This is very difficult, as it takes a long time ICly, and the game runs on a 1:1 timescale. This is why we have so few PC kids actually making it to the team. Xavier's does not want its students to become soldiers, much as they know that it's unfortunately necessary at this time. As a result, everyone is going to be encouraged to graduate, go off to college, university, or trade school, and live the Xavier dream of integration into society.
However, some students will show promise. They're the ones who can pull it together in a crunch, who are dedicated, who are realists in their view of the world, and who are, on the whole, good examples for the other students to follow. (Well, within reason. Please do not attempt to consume as much sugar as Jubilee does.) Those students will be approached some time between their sophomore and junior years and asked if they'd like to take some extra training with their abilities, beyond the simple control that everyone is taught. For the remainder of their high school years, dependant on their ability to keep good grades and behavior, and keep the rest of their life balanced, they'll take training in the Danger Room.
Upon graduation, they'll be encouraged to take a year or two off, get some higher education, and think seriously about whether this is what they want to do with their lives. If the answer is 'yes', then they'll be inducted into the team, usually in the form of being told out of the blue that there's a mission, get down to the ready room and get a suit.
Joining
Characters must RP their way into the X-Men. Because of the nature of the group, this is generally a long process unless a former history has been established. If you're interested, please talk to a member of Staff. If this is a long-term goal, it's usually a good idea to talk to those involved early on. Interest in and of itself will not guarantee acceptance into the organization. Since the role of the X-Men is so sensitive, only characters that make sense as X-Men will be able to make their way into the group.