kif, i am very happy to hear that you did not have to see a professional about your daughter. I am starting to try the things that you had done. Thank you.
The best help you can offer is to be sure to keep your son in the mix, so to speak. That is, be sure he has opportunities to interact with other children outside of school. This is particularly helpful in recreational settings.
Is seeing a professional the only answer? What about when two parents work together with the child? What are some suggestions we as parents (separated) can do to help the situation?
My son (3yo) is a natural social creature - he just wanders up to random people and starts babbling at them about how they are now his friends and he sure does like his friends. My daughter (5yo) is not naturally sociable. At a park she will generally do her own thing and if another child attmepts to be sociable she will give them the evil death glare for interupting...
But at around 4, she started refusing to go to the park because she said "Those other kids don't like me". My first thought was to point out that she had all but been hissing and recoiling like a vampire at sunlight anytime she was approached for two years... but then of course motherhood got the better of me and I realized that the processes of being friendly that came so naturally to my son were alien to her. I set out to *teach* her how to make friends.
It involved me approaching people and making a buttinski of myself instead of her. I would approach similarily aged children in parks and ask their names, ages, whatever... and then "introduce" Eowyn and set them up for play: "Eowyn was going to play on the slide, would you like to play with her?" Then... fade into the background. Sometimes they got bored of each other rather quickly, sometimes I had to tear them apart screaming to get home in time to cook dinner.
But in the end, by sheer repetition, and because I took the pressure off of her, Eowyn figured out how to make a basic introduction for herself. She is still not a social butterfly, but she has a few more tools to help her make do.
It's unusual for a first grader to be excluded, unless he is behaving in a way that is off putting to the other kids or, as you suggest, he's incorrectly perceiving that other kids don't want him around when actually he's keeping his own distance. These things tend not to be phases, and they can become habit patterns in relationships. Professionals can discern how a child perceives himself and the world around him and how he responds (emotionally, behaviorally) to those perceptions. From this information a plan for intervention can be designed.