I'm almost 21 and I've been a T-1 diabetic since I was 4 1/2. Is your son on the pump? If not, he should definitely work towards it. It will do him a world of good in helping to control his blood sugars. I know for me, when things get easier, I am more inclined to take care of myself. I used to take Lantus and a bolus of insulin every time I ate and it was terrible. Sometimes I found myself skipping insulin doses...not because I didn't care about my health, but because nobody else around me had to take shots. That's probably the worst part about diabetes - that so few have it and you always feel so alone when dealing with it. I've met a few other diabetics and talking with them is such a huge relief. I guess its like the difference between talking to someone from the city about your chickens, or talking to someone else who has pet chickens...its just easier.
You might want to look and see if your hospital or endocrinologist has some sort of group or summer camp he can go to so that he can be with other diabetics. Also, make it very clear to him what will happen if he doesn't control his blood sugars. Not just death...that's not always scary when you are 15. The things that ARE scary is thinking you could end up in a wheel chair someday...or worse, lose a limb.
And don't let the school treat him differently because he is a diabetic. Not being able to ride the bus because he is a diabetic is a load of crud from the school. IMO that is downright discrimination. Oooo...I have so much more I want to write, but I have to run to class. I will try to finish typing up my thoughts after class! Please don't hesitate to ask questions though. I love educating people about diabetes, especially since I grew up with it.