You're son sounds like he has a very good grasp on things overall.
My daughter gets test anxiety. She can know something inside out and fail the test. She's learned how to deal with it and gave me great pointers before I had an important test last year. College most likely isn't for her - her call on that. None of us have a problem with it. She has many interests and is a valued employee. She's currently a military avionics technician.
Have you ever read about different types of geniuses? Not everyone is adapt at fitting into the mold traditional schooling works on. That's OK.
Multiple Intelligences byÂ* Dr. Thomas Armstrong