This is a very difficult situation. I bet your son is at an age where he thinks he is invincible, knows better than his parents, does not want to feel different or excluded from his friends and might be suffering from burnout. You can encourage him to test and take care of himself, but ultimately he is the one that will have to do it. I think you need to work on changing his outlooks to get him to take his management more seriously. I have some suggestions and maybe one of them will hit home with him...
First off have insulin available at the school, in the nurse's office in his locker, just somewhere so that if he wants to take care of himself he can do it easier. Second see the endo 4 times a year. With an A1C that high he needs to see an endo who may be able to get him to take better care of himself.
Who is the main one in charge of diabetes management, him or you? Is he aware of all the ways/information to treat T1? He may benefit if you say something like, your becoming independent and in a few years you will be off on your own at college. I think it is a good idea for you to take control of your management and let me take a back seat. This may empower him. Also, you could schedule a meeting with a dietician, CDE, endo, etc. at this point to make sure he knows how to accurately care for himself.
Possibly some reward for testing and/or bolusing? A dollar per test no matter the result. If you do this don't criticize the numbers, just reward the behavior towards better glycemic control.
He could be the type of kid that just wants a break. He may find it very beneficial to see that you are on his team and he is trying hard. You could do this by compliments and positive reinforcement. Or getting his supplies out and ready for him. Or counting carbs for him when he is around so he can "escape" for at least a little bit.
I would also seek out other sources than his parents for him to learn, see or be around diabetics. Sometimes at that age the last person a teen will listen to are their parents. Weather its an endo to educate him, or a support group for diabetics, or a T1 camp.
Fear is also a big motivator for people and scare tactics could be considered. I am not a fan of this idea as it could easily do more harm than good, but for some it may work.
Good luck. I was a bit defiant in my teen years and my management laxed. This is, to some extent, normal T1 behavior but you are doing the right thing by tyring to help him be able to lead a long and healthy life.