One of my kids had a very similar profile at that age. She was diagnosed with something called a non-verbal learning disability. Like your son, she was quite articulate, and we had some trouble getting a diagnosis.
Here is a pretty good website on it:
http://www.nldontheweb.org/ My kid is now a freshman at college, and while she still struggles with organization, she seems to be holding her own. Just so you know that if it turns out that his is your son's issue (or part of it), that many of the challenges can be overcome. Also, my D is actually in a math-related major -- she is good at math, although has some slow processing speed issues. So even though her test scores are lower on the non-verbal side, she is actually pretty good at math and is pursuing a STEM major.
