Good lord, cut the boy some slack! He hardly sounds like he's out there mugging grannies and shovelling mephedrone down his neck like some Daily Mail vision incarnate!
"He just seems to have a mind of his own right now"
That's exactly what he does have! Part of the process of puberty is growing into the person you're going to become and moving away from the child you were. This will inevitably involve the testing of boundaries - getting up late, staying out late, not tidying his room... And really, if he's already 15 and this is the worst he's doing, you're getting off very lightly! Not to belittle your stresses, but it sounds as if you may be slightly overreacting. He'll learn from his mistakes - be that socially, or academically - but he has to be allowed to do so. The best thing you can do is give him some room and be there for him when he needs you. Growing up is a learning curve for the parents, too, and a pretty steep one.
If you really feel you need help with him, ask the one person able to provide it - your son. Take him out for lunch somewhere, just the two of you, and, as you would an adult, ask him how he is and how he's finding things. Chances are taking a step back will work wonders for the both of you.