Realizing that there are consequences for
your actions is usually not a strong point for
someone with ADHD
, at least at his age. Maybe by late high school.
There can be good reasons to hold a child back. Just don't make it that he will learn a lesson. If anything (assuming it happens), you DON'T want to treat it as a punishment, but as an opportunity to get ahead. If you take the negative route with being held back, I personally and professionally believe that you will regret it.