Tank not Happy mean Mommy

The Tank has been grounded for about a month or so.  No I-pod, no friends, no fun.  He is a great kid and helpful when we ask him to do things.  He is not a trouble maker, nor does he have a sassy mouth.  His problem is laziness, pure and simple. He is a very intelligent young man.  About a month ago I get a progress report the shows a D for biology. Ok stop a D, you have to be kidding me.  So I go on Zangle and check his grades and he also has a C and and E (this in health) REALLY.  This is totally unacceptable it has always been B or better.  Now if he did not have the ability we could understand.  The Tank's problem is not turning in assignments.  So I e-mail all of the teachers to make sure these are his grades and yes of course they are.  The teachers tell me he has a lot of work that is missing and he can turn it in for half credit.  So I am fuming.  I write down all missing assignments from all of his classes and ride him everyday to finish, redo or start from scratch to turn these in.  Today Tank comes to me and says "When do I get my friends?"  to which I reply "What?" and he says "When can I hang out with my friends?"  I tell him that I am waiting for his report card because that is why he is grounded in the first place.  He is upset I can tell by the way he just looks at me and them walks away.  I am proud of him because he does not argue or get really upset.  These behaviors are totally unacceptable and he would never do them.  But so is a D or an E but he is doing that behavior to get those grades.  So how long can a teenager be mad at his parents?  HA trick question they are always mad at their parents.  Little does he know I am upset too that he is grounded, and has less than a B.  We were planning drivers training for the summer.  That's off for now.