My son skipped 2nd grade partway through the year and it was not without some social struggles. First he got picked on by a child much bigger than him and my son is not very assertive. Then my son seems to recognize the 'cool' popular, athletic kids and seeks out friendships with them. He tries to be one of them and it's hard for me to witness because he is not an athletically-talented kid, especially compared with a bunch of much bigger kids- they are not mean though and seem ok with him. He was more of a leader in his old class, now he's trying to fit in.
Overall the grade skip was justified. He is still at the top of his class, although now he has some peers that are near where he is. Math is still an issue, but I figured we deal with one thing at a time and not press for further acceleration.
The social issues are very valid concerns. I would just take things as they come.
