I was pretty sure I was about to get in trouble when I messaged "wake up" to a kid that fell asleep at his computer and he called the teacher over. The computers were named numerically and in the same order they were laid out in the room, so they could have looked at the printed label on his machine, and the name of the machine the message came from, and counted over to me just as easily as I counted over to him, but they just puzzled over it for a second and dropped it.

A friend at high school was suspended after discovering the whole district shared a network and spammed our rival school with messages.