I have the same problem. My grades don't slip but I get a hell of a lot of complaints from my teachers. I plan on trying to force myself into doing the work before going on the computer.
get hi then do homework.. it kills short term memory (which for me) makes me forget about doing soemthing fun, weed also makes me slightly lazy which helps alot when I am eating roman noodle soup while quickly finishing a geometry assignment..
Eh well my answer is like most; Push yourself. Forget about the computer, I had the same problem, and I sorta still do but my grades are good. I can spend a whole day in front of the computer on a weekend and I will probably only get a B if not a B+ for a test.
The computer won't help you earn the money needed to pay for the bill when you have your own place.
Maybe do homework on your way home? or before you leave school?
If not, it's obvious you need to cut back on the computer usage time for a bit when you get home and dedicate it to doing homework.
I think you all would need to use less computer and more working days =)