My 14 year old daughter is on vyvanse and so far it has been the best for focus ,and we have tried numerous ones. It might be two things , maybe your son needs a medication change? I have been told by professionals that over time the meds become inaffective and that the body gets “used”to the drug. Not sure if that’s true, but I know as hormones change etc…. dosages might need tweaking. The second being that his dose in the a.m is early so the drug wears of earlier? I’m sure you have thought of both. Parents of kids like ours are constantly trying to juggle things and read into what is going on in our children.
I feel like sometimes I know more than my Dr about this. Lol