"Zone of Proximal Development" [1]
Montessori schools do this.
[1] - https://en.m.wikipedia.org/wiki/Zone_of_proximal_development
Even trying to rely on outside media, it's still much more labor intensive for teachers.
And you need a more motivated student body than the typical middle school or high school student. The small quizzes you include to make sure that students consumed the flipped content beg for exploiting and cheating, even with randomization.
Finally, it's not really clear how well it works. In general, K-8th work away from teacher supervision shows no evidence of benefit, and the educational research we have on the flipped model is mostly of poor quality except for a couple of good studies of undergraduates.
Education tends to have big "trendy ideas" that have some plausibility that they'll work and excitement around them and a whole lot of administrator support and profe$$ional development services spring up around them. And then you have people endlessly debate the merits based on personal experience.
(I'm about to teach a microeconomics class where I'm going to flip 1/3rd of the lessons in a private high school environment with a relatively motivated student body; the motivation is so that I can fit more simulations into an already-very-dense AP curriculum without an infinite homework load. I've become a relatively successful middle school teacher of engineering and mathematics enrichment classes over the past couple of years and I struggle to see how I can flip much successfully-- so much of my success is around social pressures that come from interaction of students with each other and their teacher).
It may not be inevitable. Personally I had pretty great experiences with multi-grade clubs, camps, sports teams, classes, academic competitions, after school programs, etc. (not to mention the neighborhood/real world.) The older kids were usually pretty nice, often really helpful, and provided a kind of role modeling.
Sports teams can sometimes be kind of hilariously unbalanced due to the drastic difference in sizes of some kids though. Perhaps some sports should be sliced into height or weight classes rather than age classes, but that's probably only practical for large leagues.
That’s a nice thing to wish, but at least in the public school system in the US, it’s no longer something that you can expect depending on the region. There are many reasons for this both including indifference and / or just being overwhelmed.
Athletics should be separate from schooling and run by the community (as is Europe).
This was not an argument for school athletics. It was an observation that age quantization-- whether by schools or by private athletic leagues-- makes a big difference on the trajectory of athletes. In turn, you have from age quantization alone pretty big physical differences in students of the same nominal age.
Your comment is completely orthogonal to what you replied to.
Individually you feel pressure to move into the best school districts. Yet collectively it falls into racial boundaries because of decades of systemic racism.
Forced busing suddenly fixes a lot of the funding biases, but is very unpopular because fear of the other is hard to overcome.
A more reasonable school, after the elementary level, should mix and match kids, so that older kids with more advanced skills could help those who hasn't still advanced as much. It should allow to take courses, much like a college does, in whatever order a kid (and their parents) find most beneficial, independent of the age, with the goal to pass a GED test by the end of the school. Even better, it should be possible to pass a basic or an advanced level of a test for a subject, independent of the age. The presence of several parallel tracks for a subject solves the issue with gifted kids and struggling kids alike.
I don't think I have all the answers, but the standard school education system was invented in Prussia in the middle of 18th century, and is pretty obviously inadequate for today; ask teachers, students, or parents. Though maybe for some parents it looks adequate because it functions as a storage facility for kids for the day. But kids could spend their time much better than that.