BTDT, last 2 quarters with GS10! I finally told the teachers that GS10 has to take ownership of his schoolwork and I would no longer sign his planner if he had no involvement in filling it out. His assignment grades were painful to see, his tests were still A's.
I told GS10 if he turned in everything this quarter, and filled out his planner I would get him a DS Lite. GS10 does not respond to withdrawal of privileges, (except limiting The Simpsons) but responds to rewards. So far, so good -- this quarter. And he is feeling better about his organization, too.

Btw, does your child have a very messy desk at school? GS10 did, and when I implemented my new plan I went to school and cleaned out his desk & cubby. He was humiliated enough he's not letting it build up again, but now so bad that anyone teased him. His teacher really appreciated it, too.