X-Men #1

Uncanny X-Men (1963) #1 This is where it all began. It's the X-Men vs. Magneto! At Xavier's School for Gifted Youngsters in Westchester County, New York, Professor Charles Xavier summons his students telepathically. When the Beast, Angel, Iceman, and Cyclops arrive, he puts them through a series of exercises to hone their mutant talents. Xavier then introduces them to a new student, Marvel Girl "Jean Grey", to whom he explains the purpose of his school: his students do receive an education, but they are also the first line of defense against evil mutants.