Do you have time to volunteer at his school? I find it that schools are much more willing to accomodate your needs if you yourself will come up with some ideas and get other parents of gifted kids to work with you. I know that some of us here will blurb that this is not how the system is supposed to work but I look at it this way - instead of working with my child at home on more diffucult topics so she/he is challenged (and challenged they have to be!) I would much rather do it during the school hours. If you get a gropu of a few motivated parents, you can create your own gifted pull out class. This solves the problem at least temporarily, until he gets to go to this "good" gifted class. Look up www.aleks.com, www.beestar.org, www.learningexpresslibrary.com - those are all either free or very inexpensive programs that can help you in such an endavour. But even making them read a more difficult book and discussing it will be motivating.
Good Luck,
Ania

P.S. And the fact that they do not want to go to school is never ending for some kids. My son was just home sick for a couple of days, and eventh ought his school challenges him and he is thriving, he made a comment, after watching science channel for a few hours - "I would learn more if I stayed home" :-)