My school has a haunted basement. There's a door that teachers have the only key to, and I got to go in the room one time to film a school news video. It's really freaky. The building used to be a gun range before it became a school in the 1950's, so there's bullet casings everywhere on the floor, spiderwebs, and desks from decades ago. It has a really creepy feeling to it.
If that's not freaky enough for you, a couple years ago a homeless man broke in over the weekend and somehow got into that room, even though the janitor thought he locked it. His break-in doesn't even show on the security cameras (I find that part hard to believe, but whatever) and when our janitor found him, he was screaming about something chasing him.
I've seen creepy things here, like how there's one section of a hallway that has never had lights turned on while I've been here. In that same hallway there's a sealed box between the lockers, and even though some people think it's for maintenance, I checked and there's no way to open it.There's a bunch of teachers that swear they've heard spooky things.
That may not sound convincing, but it's the best one I've got for now. If I think of another one I'll let you know