When I was in high school (1990s), my friend Mark removed the top sheet-metal ceiling from his locker and discovered a phone line going past. So he tapped into

When I was in high school (1990s), my friend Mark removed the top sheet-metal ceiling from his locker and discovered a phone line going past. So he tapped into it and, to my knowledge, became the only kid in school with a phone in his locker. It was used for prank calls, of course.