D.,
Have him evaluated by a neuropsychologist. You need to know if there are any unidentifed issues with his processing. What you are seeing is extreemly common for very bight kids who are suddenly overwhelmed by school in the late elementary, middle school, junior high school time frame. They are smart, and they suddenly have an issue that they cannot explain, and since they have always done well, and cannot for the life of them figure out how to bypass this issue and find success, they act like they don't care. It is easier to admit that they don't really care when they are clueless about why this is happening, and they secretly think that you have been lying to them all along about how smart they are...they may have had some massive coping strategies to overcome mild issues that have just caught up with them and they can no longer overcome and succeed, and nobody has noticed because they have superior skills in some other region that was able to carry them over, but now they need some targeted intervention to help them develop new stratgies.
This may be out of pocket, but you need to own this information for yourself. The school is responsible for his education, so if he is on the verge of failure, he should be evlauted by them as well, however, do not count on them getting to the bottom of this as quickly as you can. You should never know less than they do anyway, so invest in your son and get an private evaluation that will keep the school honest. I would be willing to bet that there is a major dip on one area of his processing that is causing this issue, and once you help him with appropriate services and therapies, he will change his tune about not caring.
Call a neuropyschologist, and write the school and ask for an educational evaluation to determine your son's needs for targeted intervention services to keep him from failing. Anything you do with the school needs to be in writing, if it happend over the phone and you cannot hold a copy of it in your hand, it never happened at all. Write.
Log on to www.wrightslaw.com and learn about advocacy, and you might pick up a book by Dr. Mel Levine called "The Myth of Layziness" you may see your son in the pages.
M.