Welcome DawnKO!
I was skipped in Montessori as well - to 4th grade from 1st. I recall being socially isolated the first few days ( I was so small), but recall having fun after wards. I went back to public school - who did not skip - after that and recall it was a very painful time with a lot of clashes with the teachers. So don't think PS will be a step up.
I was involved in a lot of sports at that age - baseball, football, soccer, etc - so I had age peers I could find common ground with. I was also involved in Cub scouts. This helped me a lot. Later on I got involved in adult-level clubs that matched my interests and found adults who I could relate to. There could be programs at local museums that your DS would like along these lines. Once he finds someone he wants to interact with, he will listen..
