My son, among his other problems, has also been diagnosed as ADHD. We got him started in Special Ed. in second grade because, in our district at least, SpecEd kids have access to what they have called a “Resource Room.” It has some other name now, like “Learning Center” but it is the same thing. It is in essence a class of two or three students at a time and focused on whatever particular subject is the difficult one. My son went to resource classes for reading and math.
A lot of kids with ADHD have problems with noise. If your son has an IEP it can specify that he can take tests or do concentrated work either in a separate and quiet room or with noise-blocking head phones. If need be, your son can even be assigned a paraprofessional to help him focus and to redirect him.
I also strongly recommend that you get a good psychologist. Such a person can help both you and your son develop coping tools to deal with ADHD. These can be ways to break tasks into smaller segments which you can then check off a list when they are finished, reward systems that help him have a reason to work hard at focusing, and other methods of coping. Your pediatrician can continue to prescribe the ADHD meds, but if they don’t seem to be working you may want to find a psychiatrist who is more familiar with the effects and the pros and cons of other ADHD drugs.
Also, many ADHD kids love the computer and do well with it, especially since many of them have terrible handwriting and spelling. Thus, a program like the one daloon mentions could be a good thing. My son loves computers and actually got started on them when he was three. ADHD kids also often like adrenalin rushes. Sometimes getting them involved in a very active and fast moving sport such as soccer or basketball can help their self-esteem as well as release pent-up energy and so make it a bit easier to focus.
And as you already suspect, as kids grow the amount and sometimes the type of ADHD medication needs to be adjusted. So far for my son the best one is Metadate, a time-release version of Ritalin. Adderall and Stratera did nothing for him, although they work well for other kids. Psychiatrists are often more up-to-date on these drugs than are pediatricians, but you may want to talk to your pediatrician to see if she follows this research or if she would refer you to a good psychiatrist.
Good luck! I have known some very successful adults who were ADHD. One in particular was a co-worker who broke all her tasks down into short sections, made a list of them, and then checked them off as she completed them in random order. By the end of the day she invariably got more done than anyone else in our workplace. Another became a surgeon and a marathon runner.