Diane,
By law, they HAVE to accommodate your gifted child. But believe me - it doesn't mean they will make it easy for you. We are in PA as well, and we have fought for years for things for both our kids who have GIEPs. We have found the GIEPs to be largely useless documents. BUT...that doesn't stop us from fighting. It doesn't matter that the times don't line up. It is their responsibility to educate your child based on his present levels. DO NOT let them change his GIEP just because it's not convenient for them. YOU are really the only one who has your child's best interest at heart. Recent school budget cuts have had them cutting wherever they can, and it you let them, they will happily cut our your son't GIEP to save some $$.
Our school district wanted us to have our daughter skip a grade. We discussed it and decided we would not. Her birthday is in July and she's already one of the youngest in her class. When she was in 5th grade, she walked next door to the middle school every day so she could attend a math class there. It didn't totally line up with her 5th grade time for math and her 5th grade teacher was to catch her up on anything she missed. Quite often that didn't happen. There would be tests that she wasn't aware were scheduled because her classroom teacher neglected to tell her what she missed (as she was supposed to do.)
We have had countless meetings over the years to advocate for our kids. The elementary years are very difficult for a gifted child. I don't think our kids were ever challenged enough in elementary school. They kept telling us the kids would be challenged in high school, but that doesn't do you any good when your kid is 6!! I think one of the reasons my 16 year old hates school is because he was so bored early on.
If you are in a good district, it will be better in middle school and high school when there are advanced and AP classes. Unfortunately, in elementary, you just have to keep fighting for your rights. If you think they are not meeting the law, you can request a hearing. Usually, threatening to have one is enough to get the school to take you seriously. If you are inclined to pursue it, you can get an attorney involved, though that can get to be quite costly.
Does your school district have a gifted parents support group? Ours does and we got a wealth of information from there. If not, have you tried PAGE?
If you have any more specific questions, feel free to PM me.
Good luck. It's not an easy road.