I'm sorry you feel so sad too. I have those same mixed feelings about my little ones. When I got over the GT denial thing with my little ones, there was something I relized right off the bat. That is that you as the parent have to make sure your child gets the education he/she needs and deserves not the school (I know some will disagree). but I really beleive a parent has to be proactive in their childs education.
Now that you have that weight on your shoulders and trust me we all do, it sounds like you are already taking steps like testing to do this. You may find that you may have to change his schooling, I don't know what options you have , but maybe consider a private school that fits his needs, or a gifted school, or if you are able home school. Or a combo of those. I think what I'm trying to say is there are options it's just finding what works and what will challenge him. Good Luck , and yes that was a pep talk...