First there are new studies that show that a combination of stim meds and therapy allow for smaller amounts of stim meds to be given and the effectiveness is just as good.
Second, as another poster has stated, the meds can be tailored to the situation. There are short acting and long acting meds. He can take a short acting one and have it out of his system by 1 or 2 in the afternoon.
And, I agree with ADHDMomma, if it affects his concentration it is too high a dose.
Fourth, the sport does make a difference. I wish you had said which sport he was into. for example, I think that in something like Baseball, the meds would be very helpful. In Tennis, not as necessary, but really should not make much of a difference. However, in all cases, (as with all of these meds) it takes trial and error to hit the right amount.
Finally, if he is really a good athletic – where do you want him to go to school? A state school or someplace like Stanford? He will need the meds to help him in school ( and to help prevent anxiety, depression, and self medication (vis-a-vie Phelps). The point being that school, and friends, and maybe even sports can be helped with meds. You just have to take the time and research to figure it out.
But, most importantly, you need to make sure that he is aware what is going on and the reason for the medication (if you go that route).
Hope this helps.