I got downstairs and nobody was there. Dead quiet. Not a sound. the voices stopped as soon as I reached the bottom of the stairs, like I just walked in on a conversation they didn't want me to hear.
I went back upstairs. A few minutes later it started again. It got louder, and louder, and louder, and louder, so I went back down, thinking I had just missed them.
Whenever I'd go back upstairs it would start, and whenever I went downstairs it would stop.
It happened several times, and on several different occasions. I thought it was just me, but finally i asked somebody about it, and they experienced the same thing. Several people had the experience, not just me. And whenever I was downstairs in the dark, I could sense I was not alone. I could literally feel it. There are several classrooms with windows, but they always keep the doors shut, so in the hall it's pitch black.
It's really creepy.