I was diagnosed early, around age seven. At the time, the only real coping mechanism was Ritalin and very distressed parents and teachers. It took a couple of years for my parents to relent and give me the drugs, but no real coping either. Not that I blame them, in the late 80s there wasn't much outside of the drugs. It worked for me in school, but at a cost. No emotional output, no real friends, I was a zombie.
While I'm going on about my problems, what I want to say is that there are now better medications AND coping methods. Productivity managers, therapy, everything I wish I had as a kid. Get the kid into all of it as soon as a problem is forming and don't be afraid to help indulge an interest.