I used to work in a child an adolscent mental health unit, which is where im speaking from because as a mother my child is not old enough to compare notes with you. But speak to the school find out how he interacts in class and with the other students, talk with him and see if he will tell you why his not interested and if anyone has bullied him or anything similar, then after those speak with your dr and get a refferal for a child and adolscent phychiatrist or pyschologist. You can also try getting someone he trusts and respects outside the family to talk with him. sometimes kids the age of your son are more willing to open up to someone that they are not related to. good luck. let us know how you go.

Could have a problem with depression?  Have him checked out by the doc to rule it out.  Sometimes it manifests itself in ways you wouldn't think of. 

My son went through this stage and I actually found that going to the school and talking to the teacher, principal, really got me a lot more authority with my son as I found I needed some backup and they helped us to make a plan. They called in the school councillor to help too. My son was in high school and they have had the experience of so many teenagers going through there and they can really help. My son lost all his motivation to do homework and even to attend school. They have to know that there is consequences for there actions and the bigger picture of where they are heading or could head if they don't take responsibility for there own actions and the more people standing beside you and him to help him see that the better I feel. Before that I felt out of my depth. I have been there and they are very smart. He will not show you that it matters that he is grounded. He needs to know you are both on the same side. Give and take. My son is lazy and will try to get out of doing everything too, but if he wants to go and do something and he wants me to co-operate he needs to do his bit before he will get me to give him the money or the transport there. Hope this helps but mainly I am saying, seek some help and support from the experts if you feel that it is not working. It will get worse if you are trying to deal with it on your own.

Hi there, you specify the punishments that you have in place, but you haven't clarified what type of rewards you have offered. 

1.  Does your son have an input in regards to the rewards available?

2.  Do the rewards equal the task required to receive them?

3.  Is his life really any different whether or not he gets betteer grades etc.

4.  Not going outside to play, (or pursuing any healthy excercise), should ever be considered as a punishment.

5.  This is a very important time in his life, where he is transitioning into a man.  Perhaps you need to deal with him on a more adult basis and negotiate rather than dictate, (if you haven't already).

my son who is nearly 12 acts like that a lot lately, and I personally think that he DOES care, he just doesn't want me to know it! I try to remember how I was at that age, and I remember that parents are annoying and embarrassing and don't know anything! I am lucky in that my son and I can talk about anything (at the moment!), and he usually will tell me what is wrong and why he is acting a certain way. I basically just try to understand that he is ~ a. male, so is waaay different to females,,, b. at that age where he has so many hormones and emotions going through his head and body, he is probably not sure himself sometimes why he acts the way he does... I actually did up a reward chart for my elder son, and when he does everything he is supposed to for the day he gets a sticker, then at the end of the week he gets $10.00 if he has all the stickers. I ended up doing that because he just would not brush his teeth or hair or make his bed  or do his chores without a massive argument about how he doesn't care if his teeth/hair/chores/homework aren't done... I told him that I am not going to argue with him, he lives here, he is part of the family and he needs to help with chores. I also told him that I love him, but I am not going to put up with being treated like that, and he needs to do as he has been asked, otherwise I will not do what he asks, like buy new tubes for his bike or buy the cd's he likes.... Lucky for me, my Jake is not too stubborn!!! And the rewards chart is working, even though it feels like he is too old to have one!!!!  Try to have a talk  with your son, and maybe tell him how you felt when you were his age... A counsellor once said to me that what we consider very minor, may be very major to a child... Maybe he feels like you wouldn't understand and so finds it difficult to talk to you, but he needs to realise that just because he is "going through stuff" right now, doesn't mean he can do what he wants with no consequences...  I try to be understanding with my son, but at the same time a bit strict, so he knows where he stands and will respect me. hopefully!