Located outside Salem Center in Westchester County, New York, Xavier's School for Gifted Youngsters is publicly known as a prestigious boarding school, providing an outstanding college preparatory education to middle- and high-school students. With a rigorous academic curriculum and a low student-to-teacher ratio, Xavier's sends students on to the best colleges in the country.
As of August 2015, Xavier's has gone public with its additional purpose -- Founded by its current headmaster, Charles Xavier, in his family's ancestral home, the school serves as a safe haven and training ground for young mutants to learn to cope with and control their powers. Alongside more typical high school classes, Xavier's students receive instruction and guidance from the faculty in responsible use of powers and the ethics of living with them.
A note on recruitment to Xavier's School: As of the 2015-2016 school year, a simple google search easily turns up plentiful information about Xavier's, including its purpose as a place for mutant children to get a safe high school education including help controlling their powers. Given the enormous deluge of response from desperate mutants & parents clamoring to get in after going public, Xavier's no longer recruits students themselves. If you want your student to go to Xavier's, do not wait for an X-Man to turn up and recruit them! Plenty of people ICly will likely be glad to give them information about the school, but the only way to go to Xavier's is actually very simple -- fill out an application, like any normal private school!
For background-crafting purposes an added note: these days, with the enormous amount of people needing to get in, Xavier's does have a tendency to prioritize mutants who cannot be in regular school for other reasons (out of control powers, harassment) as well as a slight prioritization on mutants whose families can... actually pay full tuition without financial aid. They gotta keep the lights on, after all. If your kid can pass as human and their powers are fairly well under control already, Xavier's might not be the place for them.
Please make sure that if your character is applying to Xavier's you also let game staff know OOCly so that they can help facilitate your approval & faction change process!
Also founded by Professor Xavier from the ranks of his most promising first students, the X-Men take a still more proactive role in furthering Xavier's vision of peaceful mutant-human relations. Whereas the school does this by teaching young mutants to use their gifts safely and ethically, the X-Men do this by working to protect the world, even those parts of it that hate and fear them. A team of highly-trained mutants, the X-Men work both to combat persecution of innocent mutants by humans, and also to combat mutants who use their powers in hostile and destructive ways. Many but not all of the teachers at Xavier's are part of the team, though it also includes others -- former Xavier's graduates, or mutants who have allied themselves with the school. An open secret among the student population at the school, students are not allowed to join the ranks of the team until graduation.
Though many of the teachers at the school are X-Men, it's not required! You can play a teacher who is not an X-Man, and many people have done so! You can also play an X-Man who is not a teacher: several XS alums have gone on to be X-Men but have other full lives outside the school.
For those who live and/or work at the school ICly, the following pages provide useful information that your character would be familiar with.