More free play is not exclusive with school. More free play does not solve ADHD. ADHD kid I know have hours of free play every day and he still have trouble to behave in school - while other kids don't have such problem. He has good days and bad days and that is not correlated to type of work. And when he has bad day, the other kids in class essentially sit bored waiting, because all teachers attention necessary goes toward that one out of control kid (he is too disruptive to be just ignore when he has that). When he has good day, he is fine boy trying to please those around. He is trying to not have bad day I think, he seems unable to.

Also, while there are some shitty schools with "forcing small children to sit and focus on unmotivated externally assigned busywork while being passively monitored by a stressed out and outnumbered authority figure", ADHD happen in non shitty ones.

When kids universally hate the school and there are problems with everyone then it is one thing. When there are few kids who behave differently then other kids, then we maybe should accept that there is something different about them. Because that is the thing - many many kids like to go to school at that age. Or are indifferent to school. Or don't like it, but don't have problem to sit while class is going on. And some kids have problem to control their behavior regardless of whether they like the school, teacher and other kids.