How long do you have till midterms? If all your classes are really easy and you are getting all As then I would suggest advisor meeting and push to get you moved up to harder classes before it is too late. Junior year load tends to be the hardest so that seems odd because even if not AP classes should be challenging and interesting. As for the social stuff, is it really a problem to be friends with sophomores? If you get along and enjoy their company I see nothing wrong with it. Are you doing a sport and some clubs? That would be a good place to make friends too. And I get the desire to go home and sleep in your own bed but you should try to stay on campus once in a while. If your school has Sat classes, Sat night is the main social time when there would be good opportunities to meet other kids and make more friends.