Some people can’t handle going off and on stimulants like that. My son couldn’t. If he had a day off of his medicine, it took two days back on it to return to his “normal.”
It could be something else entirely. Something troubling him at school. Bullying, anxiety, etc…
Could be time to try a different medication.
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism