Teachin' How to Keep it Real

So as a warm-up excercise I am teaching the kids SLANG. The first week, I taught the kids what "What's Happenin'" means, and last week I taught them "'Sup". It is hysterically funny and basically gives all the students an opportunity to laugh at me for about five minutes before class begins. Because of the challenge for them to say what's up in a matter that they can sound cool...I abbreviated it down to 'Sup. I told them it had to be said fast and in passing...and that men have to use a low voice when saying it...So now I have all these little 12-14 year old kids passing me in the hallway going 'Sup.
This weeks SLANG is "I'm Down!" For those who may not know..."I'm down" is used to say that "I am willing to participate in that activity...or please include me in the plans..." The best part about teaching the kids slang is that the teachers learn the slang also. KodomaSensei was having a helluva time trying to figure out why "I'm down" means what it does.. I believe I would be a great slang etymoligist because so far I have come up with explanations for the etymology of them all! I'm down... a deriviate of the invitation/RSVP list...hmm..makes sense right...write me down on the list please I want to be included....I'm Down!