1. Long school days mean brains are overworked and so don’t function well 2. Multi month summer breaks actively overwrite what was learned the prior year
When will schooling be built to best optimize brain power?
If anything, the only things kids learn are those that they still know after summer break, or better yet, a couple of years afterwards.
The current model is based on memorizing a whole lot of stuff and then later forgetting it. very little is learned at schools and high-schools. The relationship between invested time and knowledge returned is appalling, but it makes sense once you accept that, like others in the thread have said, school and high school are essentially grown-up childcare.
I don't mean that flippantly. Especially in grader 8/9/10 when summer jobs weren't as common. There are things you don't learn in school, and time for the sake of time is a precious gift.