We went through the same thing with our oldest when he started Kindergarten. It was our worst year ever...He was far ahead of the other children academically and had a great deal of difficulty socializing. First grade was a little better..He is in the third grade now and we've done a couple of things to help him out. It sounds like your son is probably very bright and does need some other outlets.
You will all likely disagree with this, but I stopped doing a lot of extra academic work with him at home. Instead of building on his knowledge...he could easily be doing more difficult math problems...we started doing more lateral building....german saturday school, chess club, geology club, etc, etc. This got him active with children with similar abilities and interests.
In the school they have had to work very hard to help him socialize. If left on his own, he will simply take a book out to the playground and read while the others play. So the teachers adopted a program with him that once a week instead of going to recess they would pick two boys to go to the computer lab and play a geography game together. (Andrew loves geography). This helped him a lot in his socialization.
We also faced the issue of whether or not we should skip him a grade or even homeschool. We decided to leave him where he was and focus on the socializing. What I've come to realize is that as inviting as it is for me to help propel him ahead, learning to socialize is extremely important too...at least as important as academic success.
Maybe you can sign him up for some of these 'lateral' activities in your community where he can meet like-minded young people his own age? Also..consider play dates where you can be there to supervise and help guide him if he needs help.
kris