It's true that medication cannot be used in determining disability status. Nor can the school force you to medicate him, nor withhold accommodations because you choose to medicate or not medicate him. ADHD also definitely cannot be used per se as a factor in the gifted eligibility process, as that would be clear discrimination on the basis of a disability.
To be a little more specific, his disability status is determined on the basis of how he behaves while unmedicated - whether or not you choose to medicate him for school. (His accommodation list might be different if he needs different accommodations when medicated and you choose to do that. But aeh is right that they can't force you to medicate him or withhold accommodations because you do not.)
If you have not read up on 504 plans at wrightslaw.org and/or read
From Emotions to Advocacy, I encourage you to do both.
Good luck!
