A few things.
Even if the community is welcoming and kind, that does not mean a student will feel drawn in, want to be drawn in and/or take advantage of it.
I’d ask the following. Does it bother him that he has no friends in HS? Is it you who are concerned or your S, or both? What causes the anxiety, if you know? Is he in any kind of therapy right now? A 504? Any kind of accommodations now? Any EC’s? No right answer here, just data points.
Our kids struggle with a mix of these things and various LD’s and we are fleshing out the last college list of our four, bearing many of these items in mind. Knowing a bit more will help to provide some suggestions.