Could he be "saving face" or acting a part?
For example...back in high school (in the dark ages) I hung out with the stoner crowd. In order to be a part of that crowd you had to be basically getting bad grades, a partier, etc. Ok...I could hang with doing the drugs...but I had a problem with the grades deal because I was smart! So I would "fake" failing. At least I did for awhile. I would change my grades on papers that my friends would see or tell them how bad I did, and complain about stuff.
Maybe he wants you to think he is doing poorly so you think he is part of this crowd...or he wants the crowd to think he is just like them? Who knows...teens arent the smartest bulbs in the pack!
