The first thing that helps me get through advocacy with my DS6 (2nd grade) is making peace with others labelling me a "pushy parent". Accept that it will happen - by parents, teachers, and administrators! And remember that it will be worth it in the end when you're kid has a good academic work ethic and good attitude about school. You can vent here about it :), but don't let that fear get in the way of doing what's best for your DS - you know him best.
That said, sounds like they are willing to be flexible for your DS. The tricky thing is knowing when you're asking for reasonable accomodations so that he gets "meaningful benefit" or asking for perfection.
Sounds from what you're saying that your DS is ready for 3rd grade material in a number of subjects. He's not going to get a 3rd grade education in a second grade class in every subject. One option is to move him to a 3rd grade class now, but you would have to look at all of the pros and cons of that. Others on their board have done mid-year grade-skips and can talk more about that. If he doesn't skip to 3rd now, what I would do is pick 1 or 2 subjects that you think it's important that he be exposed to accelerated material in (sounds like you have a good rationale for SS) and try to get it by writing a letter to the principal. I think it's important, though, to be open-minded in how you get it. One option, as you said, is move to 3rd grade SS. Another option is to ask the school to provide him with the 3rd grade SS materials so he could do it on his own. Is the computerized learning accelerated to 3rd grade and not just enriched? If so, sounds like a good way for DS to be exposed to the materials. If he's uncomfortable with doing it in the classroom, could he be excused during SS classtime to go to a resource room?
