What is it with 13 yr. old boys? Our son started doing that in his two English classes and it drove me crazy. He went from an A to a C in 3 weeks. I knew he was doing the assignments because I was checking them every evening. So Dad (Mr. Mom at the time) wemt to the school and talked to the teachers, counselor, vice principal, and basketball coach. Then he told our son that if he couldn't manage to turn in his assignments on time, Dad would come and sit in the classroom with him and make sure that he turned the assignments in. Picture the look of horror on our son's face <LOL>. When he learned that Dad had the approval of the teachers, counselor, vice principal and coach, he promised to turn everything in. By the end of the 6 week reporting period, his grade was back up to an A. We never had that problem again.
My husband was a HS drop out, though he later got his GED, so he understood the value of the education our son was wasting much better than I did.
Good luck.