"Voluntary" Saturday detention that the school forces you to do (like cleaning desks, windows, chairs, computers, trash, etc.) as punishment instead of giving out suspensions. Its really not voluntary, but they say it is so they can get around child labor laws. Its usually about 4 hours long and starts at annoying times like 7 or 8 in the morning.
Zach: "Shit, I forgot to do community service hours for colleges"
Dan: "Didn't you have SWAP on Saturday? I thought that was voluntary?"
Zach: "True bro! I'm gonna put those hours down on my form to piss the school off even more!"