We might also consider that children do not get enough sleep these days and are overstimulated in daycare. Of the two, I would say that lack of sleep is a factor in the ADD/ADHD equation.
Another factor is the disconnect between what a kids wear to school and how they are supposed to behave. When there was a dress code even in public schools little boys wore dress shirts and ties, dress pants and dress shoes. Since they dressed for a structured environment, they behaved accordingly. What is a kid to think or do if he’s put in play clothes and then told to sit still? He’s going to go with the idea that he’s on the playground and act accordingly.
Part of the lack of structure is the lack of, or reduction of, the authority of the father in the home.
Our pussified/liberalized culture these days denegrates masculinity and patriarchal authority,
to the detriment of children in need of such boundary enforcement.
That’s why ADHD is often referred to as “Absent Dad/Husband Disorder”.
(A pre-emptive “Keep your shorts on”: I KNOW there are genuine cases out there.)
“Another factor is the disconnect between what a kids wear to school and how they are supposed to behave.”
Not a bad thought. And unfortunately, I think that applies to everyone these days. Not just children.