I don't think I've told this one here.
About 5 years ago, I was teaching ESOL to a group of Mexican men and I had just taught them all our Halloween words like ghost, etc. and was standing several feet away from the board. The eraser on the board went straight up in the air and landed in the middle of the classroom.
There was no way someone fixed that up. I checked the eraser--no strings or anything--and the brick wall behind the room was solid.
