His ADD diagnosis is questionable, definitely get a second opinion. Definitely not ADHD if there aren’t symptoms.
Meds work for some kids and not for others. I haven’t seen any children that Omega helped (out of 3 students who tried), neither has my principal (I don’t know amount of children who she knows about).
Caffeine might help. There is some research about interactive metronome (I don’t know anyone who tried, but the research is impressive, I would try it for my child).
An interactive teacher is a must; the child must take notes, a SmartBoard is very helpful, if not a SmartBoard then the teacher should write on the board as the lesson progresses. It’s great if the child can exercise for a few minutes before the lesson.
Good luck!