I have a 13 yr old son, and whoever said boys don't have mood swings is wrong! Haha! He has had this same problem, and the last time it got to that point, I took boxes, clean everything, and I mean everything, other than clothes and his bed, out of his room. I gave him chores to do, and he would come home from school and do homework, have a specified amount of relaxation time and do chores, supper, bath, bed. Weekends were the same. Any attitude issues got met with a reminder that he was working to earn his stuff back and that the attitude would make this go on longer. It has worked :) Now when he starts getting an attitude, I remind him that he can go back to having nothing if he would like to continue and that puts an end to it. I got this idea from a friend who had a daughter with the same problem you are describing. Hope you get some good ideas to help you!