I am a teacher, Math teacher at that. I have students with ADD and ADHD in all of my classes. Some who have learned coping techniques and some, who, like your son, have not. It's important for you to do some very important things.
1) seek help from the school or a private counselor on techniques that might help him cope and with depression that in pre-teens and teens many times accompanies the ADD/ADHD because they feel like something is terribly wrong and they have no control over it.
2) change his diet--eliminate all processed sugars--get the book "sugarbusters" or "the south beach diet" and try to get the whole family to eat that, you'll be amazed at the difference it makes--it can improve concentration, reduce hyperactivity in children, lower blood pressure and cholestrol, reduce the amount of headaches and body aches you have. (and lose weight if you need it)
3) Try medicine--I know that many are reluctant to, however, in that age group, particularly with boys, you need to do something now to prove to him that it is something that can be helped and that it's nothing he's doing wrong, but something his body needs help with at them moment. Remind him that it's not for life, just until he (with your help) find some techniques that help him cope with it.
I can tell you from personal experience that every notebook I have ever owned (as an ADHD student and adult) has the front of every page with notes on it and the back with drawings/doodles on it. Our brains work so quickly that if you don't have something to stabalize you working puzzles with your hands, drawing on a paper, even doing oragami while you listen to teachers or even other students, your brain will wander to a thousand different things before it lands back on your work. You must eliminate ALL distractions from the area where you work, many ADD (not ADHD) students are OCD as well in some areas like their work station. Let him tell you what will help him, does he need his own desk, does it need to be large or small, where and in what does he want his pens, does he need wide-ruled or college ruled paper, where do his books, rules and other item need to be to not distract him, does he need one or two lamps, no lamps, does the radio need to be on to provide something for his brain to multi-task with (silence can be cruel to those with ADD as can harsh light), what kind of chair helps him concentrate (his brain will find everything wrong, so help him make a space that is his own and right for him even if YOU couldn't work that way--this is about HIM and helping him do better and feel better). you can mail me if you want more suggestions.
M.