Polarbear, I have looked for something like what you are mentioning but so far I haven't found anything that fits. I wish I could custom design a school. I do feel inspired by your DS's story, if he found self esteem in middle school maybe my kid could too. My main criteria for any school is small, similar type peers (must have some quirky kids), and hopefully have a science program since that is my son's passion.
Regarding the pragmatic language test, I had a speech pathologist give him the test, so I feel fairly sure he's okay there. He actually seems to know what to do socially, but I think because this school is a small school (only 70 in his 5th grade) that he's sort of solidified his reputation and he's pretty much done there. On the other hand, he's working very hard to fit in and maybe the fact that he's invisible is a good thing, standing out was one of his problems...