This is REALLY true in the computer science classroom. I am not out often, and try to keep it to one day at a time. I went to TCEA for a week once, and found my classroom in complete chaos when I came back.
I can't find anyone who can instruct the students at all. My criteria for a sub: there hasn't been a fight when she's been in the room, there hasn't been major equipment missing -- this year, whenever I'm out a mouse disappears. It's happened twice. Weird, but I think it is a student punishing me.
I'm worried about the Game workshop, I'll be out three days, at the end of the six weeks.