Most of time I will say nothing wrong with a young person since a teenager born in the US without his mother nation's background. Since the struggling with a youth to be forced with culture differences, a traditional education may not be used for a person who wished to be independent in western culture. May be he lost his interesting on studies because he has his talents on other skills. Studies are not the only targets for a person who may have other interests. I wish you could talk more with your son about his friends with cares. Talking studies less, and talks friends more. He will know that you care about him as well as his future. He may respect the cross-nation culture between US and here, since his mom and dad talk to him. Try to avoid to commit other ill behaviors not belong to him, he is still a good boy.