Of course every family dynamic is different and I have no idea what your relationship is with your son and how you normally do things, so I can't tell you what to do-- I can just tell you what has worked for our family and I what I personally would do in your shoes if it were me dealing with my son....
The week before Spring Break, my son made a poor error in judgement and got in trouble for something he did (I won't go into any details). He is usually a VERY good kid and this was his first offense, but my husband wanted to make sure it didn't happen again so he made a really big deal out of it. He told my son that he is grounded until the end of the school year from anything with a screen-- video games (which he was only allowed to use on weekends anyway), TV, and any form of computer (unless it was for school or scouts). We went away for Spring Break and took a cruise. In the weeks following, we noticed a change in my son. Some of it, I think, was due to the incredible amount of freedom he was given on the cruise ship. I'm not saying to go on a cruise, but if there is some way you can think of, give your son a huge amount of rope in a safe environment to show him that you DO trust him and that he IS capable of making good choices and starting to be old enough to have some freedoms he didn't have as a little kid. THEN, make sure he gets it that with freedom and privilages comes responsibilities (in the form of chores as well as school work). The other reason I think we noticed a change in my son was that once he got home from school, what could he do?? He used to rush through homework or say he didn't have any, then hop on the computer or veg in front of the TV-- and now he is grounded from both of those things. He has focused more on schoolwork (and scouts-- he has a ton of merit badges now--haha!) and has time to just be a kid, and it's almost like he's happier now without all of the electronics. We're going to ease him back into them over the summer....
Since it's almost the end of the school year, I'm not sure if you want to do this now, or wait until next school year and have a fresh start, but I suggest having a "family meeting". Our family has them when we have something to discuss, because once you call it that, you have everyone's undivided attention, with no "hurry up and say what you have to say so I can get back to what I was doing", including the adults-- and the kids love to have our undivided attention because in the rush of life they don't get that very often, right? Anyway, we let our children know every now and then that we feel like we would be letting them down as parents if we continued to allow (--insert behavior you want changed--). It's a form of "we are doing this for your own good" that our kids seem to respect. We have used examples of kids we know who are unruly-- we have a family in our neighborhood with a single dad. He has said that he puts a roof over their head and food on the table and beyond that they are on their own.... so his kids are often up to no good around the neighborhood, and his middle schooler is quite often suspended from school. My kids can't stand those kids. We use them as an example of what can happen when the parents don't care enough to discipline their kids, and just let them do whatever they want. We also know a family with a son my son's age-- this boy is very lazy and whinny. My husband has said, "Well, someone has to flip the burgers at McDonalds, so at least we can be assured that there is one person destined to do that." We use that boy as an example because we know he has no motivation and that's what happens when you have no goals or don't try hard at anything you do. On the flip side, one of my son's good friends is a straight A student, so we use him as an example of someone who will more than likely make something of himself-- not because he is handed A's for his report card, but because he works really hard for those A's. We don't push our own son to get straight A's, but he gets it that you have to try the best you can and keep your grades up NOW to form good habits so that when your grades do start to count for college you'll already have it as a habit to work hard. During the family meeting, you can ask your son what he wants to do after high school-- college, trade school, or a job (because sponging off of you will NOT be an option!!) College isn't for everyone and he has time to change his mind, so if he says he just wants to get a job (which he might say that because at his age some kids think "I don't want to go to college so what is the point of keeping my grades up now and learning all this stuff I don't need, like history and algebra)..... anyway, my point is, let him speak and make sure he understands that his goals and what he wants (or thinks he wants for now) is important to you. Make sure his thoughts and feelings are HEARD. Say, for example, he says he wants to just get a job. Without being condiscending and without talking down to him in any way, walk him through what life would be like. "OK, so you want to get a job and move out on your own? You would want a pretty decent job in order to afford to have a decent place to live, especially if you want to be able to eat more than a can of soup each day." Talk with him about how he needs to form good habits now in order for anyone to want to hire him. If he is lazy now about schoolwork, he will get into that habit and be lazy at work and his boss won't keep him for very long, then he's stuck in an apartment where he can no longer pay rent or afford to eat and he'd (gasp!) have to move back in with you! haha! Seriously, though, speak with him about what he wants out of life and help him understand what he needs to start doing NOW in order for his life to go the way he wants it to go.
