What you do, if you have a car, is this.

Before school starts tomorrow, find him in the halls. Get about 7 feet from him on the side of the hall.. and casually get his attention, and wave him over. Have him walk towards you, and have a VERY confident look on your face. Do not laugh or smile. Look him in the eyes. Bend over a tiny bit and whisper into his ear, in a very serious and commanding voice, "Give me the $55, the gram of coke, or I swear to God every single male member of your immediate and non-immediate family above the age of 12 will have one bone broken on a various part of their body. Don't make this tough on me, (insert his name)" then pat him on the back and walk off.. don't look back.

Now, if he doesn't give you the money or coke, you just mildly follow through with your promise. Just break both of his arms and legs, none of his family's. Wear gloves, buy a cheap pair of shoes.. and if you have long hair, tie it up somehow. Don't be stupid, use a baseball bat and DO NOT put any of the evidence(your clothes or bat) on the ground when you leave. Throw the shoes and gloves out the window on your way home, though. If an agent comes to your door and tries to pin shit on you, you know he's lying. Don't be stupid.

I've never had to do this because the intimidating comment I whisper to them always makes them come forward. If you don't have a car, improvise. If you do beat the shit out of the kid, you might gain notoriety and friends. Your confidence will be boosted and you can become a dealer yourself and no one will fuck with you.

Or you could be a pussy and just bitch on the forums.