My experience is extremely limited, as our school district has a no-grade-acceleration policy no matter what the ability level of a child is; there is subject acceleration but that's it. The gifted kids I know who work ahead of grade level for the most part here are either working in optional schools, homeschooled, or havce subject-accelerated by ability once they hit middle school. Just fwiw, even though elementary school is often boring for those kids, they do much better once they hit middle school and can get into more challenging courses. Back to grade acceleration, I grew up with a friend who was grade accelerated into my grade, and I have a close friend in another state who grade-accelerated her dd going into kindergarten. In addition to that I know quite a few families here who have their children in optional/charter schools which have multi-age classrooms, and who opted for those schools so their children would have a chance to work differentially according to ability. The feedback I've heard from each of these families is that the academics is the easy part, upper elementary and middle school is tough socially when there is an age difference. The reason I mentioned the multi-age classroom (which isn't specifically a gifted school, but has a high proportion of gifted students) is that they have grades 4-6 in the same classroom, and the parents who I know who loved grades 1-3 for their kids in a 3-year multi-age classroom almost resoundingly have changed their minds once their child is in 4th and is in with 6th graders - that specific age difference brings so many changes in maturity levels, beginnings of puberty for a lot of kids, exposure to different levels of things.. I'm not explaining it well, but a 6th grader can be at a very different place than a 4th grader socially/etc.
My friend who was able to grade-accelerate her dd was very gung-ho on it in kindergarten, even though her dd is MG, not PG. She was extremely concerned about boredom in the classroom, and her dd, now in 6th grade has done quite well in school both academically and socially. Her mom, however, isn't all that happy about the social things that her dd is exposed to in middle school, none of which is anything out of the ordinary for middle school, but her mom now says if she'd thought through this part of the grade skip she wouldn't have done it. My friend I grew up with who was grade-skipped, none of us had a clue in early elementary until 3rd grade when for some reason we all went around the room and had to tell how old we were and she was younger and explained why. She was a great student academically, and she did fine socially - in elementary and high school. Middle school she had some challenges with fitting in socially, which seemed to be hinged on age.
Soooo.. that probably sounds like I'm not a fan of grade acceleration, which isn't true - I think it's a very good thing and something many of our kids need. Just thought I'd throw out there the middle schoolish experiences we've seen for something else to consider. We desperately wanted to grade accelerate our ds when he was going into kindy, not just because of his giftedness but because he is a late birthday and just missed the age cut-off deadline. We were really really worried about boredom in school. We weren't allowed to accelerate him and in some ways it worked out great - I think he's in a much better place socially to be with age peers, also because we learned later on, around 2nd grade, that he's 2E with a disability, and not having accelerated gave us "extra" time to work through accommodations etc before hitting middle school and increased academic loads. On the down side, we didn't really realize how terribly bored he was until 5th grade when he just let everything out that he'd kept bottled up inside for all those years. He's subject-accelerated in middle school, has pursued independent study at home for several years, and he's intellectually semi-happy again with school etc (although he is still bored during much of the day). Grade acceleration would have at least had him a little bit more intellectually challenged, but I'm not sure it would have been a great answer. When we were looking at middle school options and I was consulting with his gifted teacher about choices looking forward to high school and mentioned my concern that he might be bored in one program, she told me that with his IQ, he's going to be bored in any of the district programs. Not a very encouraging thought! But I think it's a fact of life for many of us - there's not a good fit for high IQ kids in most of our public schools.
Sorry if that came off as a bit negative, I didn't mean for it to. If I sound like a parent who wishes she could have found a better educational fit for my child, it's because I am, heavy sigh. But he's also had a lot of fun in school at times too, and it's been ok. Not great, but ok.
polarbear