I would ask the G/T teacher if s/he can provide challenging/interesting work for the regular classroom when your child is done with the regular work or has tested out of it (if your school allows pre-testing.) Or can you send in work if they don't do that.
Thanks for this idea. I hope they may allow this. DS is bored with math but is still making errors in answers, I think just due to age/attention. So if he tests out of some things he may not have to suffer the school's drill and kill techniques.