The problem is, just because they sit there all day long doesn't mean these kids are getting an education (in American schools). My wife is a teacher, it's 80% babysitting and discipline.
20% actual education time is damned good. Getting children to sit still for twenty minutes is hard, getting them to listen as well is appallingly difficult. And after twenty minutes you may be talking but they're not listening. Even with motivated adults 20 minutes is about the limit of how long a lecture csn hold one's attention.
"Even with motivated adults 20 minutes is about the limit of how long a lecture csn hold one's attention."
A lecture is not the only way to educate people. Yes, lectures are boring, but discussions are not and in college and grad school I have been in discussions that went long past the scheduled end time for a class. There is no reason that could happen in high schools as well.
Yes, things are different below a certain age. Most people who hated school talk about how much they hated high school and perhaps middle school. There is a period of time where people start to want to think independently, but where our education system is based on teaching everyone to think the same things. Compliance and conformity are the goals in American schools; education is secondary, mostly a side-effect of teaching compliance.