Dear CFK,
I feel very strongly about your situation because it sounds like what recently happened to my DS9. DS9 is very mathematically able, knowing his times tables at 3, and everything in between. At 7, his IEP said he'd have Algebra; then again at 8. The teacher, who I really adore and respect, said he was pushing the limits of her math ability. It has always been OK because he had another math whiz in his class, they'd work together, and go through accelerated math and ALEKS. This year the boy skipped a grade to middle school and DS9 was teamed with the next best kid in the class. He started coming home with 80's and once a 50, all due to complete carelessness. I KNEW he knew the material (I've heard high IQ kids actually start Un-learning after too much repetition) but his sole goal was to get it done before the end of school so he didn't have to take it home. Plus he was disgusted, bored, etc. I met with the teacher with full chronology about all the guarantees in IEPs from yrs ago and told her specifically (and probably too emotionally) that I wanted him to be using the high school Alg 1 book. She said she'd request it. The district denied it--they're worried what they'll be able to do in HS I think. DS continued to be careless and I recently signed him up for AoPS Algebra course (Art of Problem Solving). I'm also working with my DS11 on Algebra who is PG, but the difference was AMAZING. DS9 grasps everything. He completely gets it. Much faster and thoroughly and with tremendous accuracy than his older brothers. He's so much happier and can go through the in-class stuff they do to prepare for grade-level state testing without complaint and with much fewer errors.
Long story to say that I believe your son is bored and you should take it into your own hands, if the guy doesn't recognize it and accelerate (maybe ask him to try giving him advanced work as an experiment). I'm trying to get the middle school where DS will go next year to let him take an online course at school during math time--maybe that's something for your DS?
On a side issue, I think proofs are important in math--we've all done them--but the requirements I've seen are completely inappropriate for highly gifted+ students. I feel like school has "trained" my DS9 like a puppet with showing his work, so that instead of instant answers to complex problems he was able to do a couple years ago, it takes him 5 minutes to go through all the steps and write it all down. I HATE it. Talk about stamping out drive and talent. I agree with Dottie--it's overkill. IEPs for PG kids should all have something about minimizing (or eliminating) repetition of lessons, and only a minimal amount of proofs (1 in 10?).