I haven't read all the previous posts, but here's our story, suggesting that it might be ok not to skip in some cases:
In K my son was reading at about a 3rd grade level and math at a similar level (if not higher for some concepts), and they pushed him up to the "highest" reading group with the gifted first graders, and this worked well (though the lexile appropriate books were not things he was interested in - grade school social dramas - though he appreciates them now). They didn't know what to do with him for math, so his teachers just supplemented him with challenging questions - which mostly worked, plus he will ocassionally find a topic he didn't know (measurements mostly) that is "grade level". He was bored a bit, but we decided not to skip him (he's one of the youngest in his class anyway, and socially wasn't very mature and had poor fine motor skills that made it difficult for him to write when in K and 1st, although he's caught up in both now). He eventually made some good friends in 1st and 2nd grade, who he is still good friends with now (5th grade). There have been challenges along the way - he does get bored, especially with standardized test review - but so do the kids who are above average at all. He's now in an advanced math class that is a 5&6th combined curriculum (finishing all the 6th grade topics in 5th grade) which will lead to a 7/8 combined math curriculum in his 6th grade year and algebra 1. He never had any peers in math in K-4, even among the other G&T kids. He's at a new school this year which is the combo of multiple elementary schools, and I think there might be one other kid in his advanced math class who is at his level. They're moving fast enough with new math material that even though it isn't "hard" for him, it's new, and they move quickly enough to keep him interested, but he's noticing that even among this more select group of students that he and one other kid are the only ones who are breezing through it. He's yet to be really challenged with math in terms of the official content, but his teacher is good and has extra stuff for them to do.
I have friends who skipped their kid - who was probably in a similar place academically, but with better fine motor skills, though possibly with more social issues. It's going ok - though I think the social aspect is still a challenge.
I guess what I'm saying is that it is OK to hesitate about skipping a grade. It can be made to work, though it is not easy. Skipping a grade won't solve everything either, especially if your child is more than 2 grade levels ahead, and the potential for boredom is there in the next grade as well. We'll see how it goes, but with the addition of science (with actual experiments) as a stand-alone subject and a focus on writing (that is sort of independent of grade level) and new music & art opportunities, foreign language, this year is going well, even if there are a few subjects that are not well differentiated .
