T.P.
Maybe instead of taking things away from him, try talking to his teachers. Get them involved as much as possible and be very consistent with follow-through. When I was his age I had the exact same problem - half the time I forgot about homework and/or left the materials I needed at school. Had my parents been more focused on helping me academically instead of punishing me, I know I would have had more successes in school. I was never a bad student, I just lacked the skills necessary to be an excellent student. Help him - talk to his teachers, talk to other parents to find out what they are doing to help their kids. Know what is going on at school at all times, not just when progress reports come out. School is the most important thing in his life!
Good luck!