I had a grade ten business class, it was the 'advanced' course cause the teach had a laptop with a projector hooked to it...and students used to play with the projector, since it was in the middle of the room (teach's desk was in the back corner) one time while we were taking a test, somebody next to the projector turned it on, the teacher didn't notice, and everybody watched as he browsed through various porno sites, for about 45 minutes straight.

he finished by shutting down his laptop, and he never knew what we had seen...but every chance we got, myself and a select few smart students would change the internet homepage of every PC we could get our hands on to goatse.cx (currently mirrored at http://www.goatse.org/ but don't ever go and look at it, for any reason)