Domestication. a.k.a. "Children crave structure."
We justify the domestication of animals, particularly dogs, by saying that they are much safer and happier in our homes than they’d be out in the wild or as strays. This is true. This is only true because our species has domesticated a large portion of their species. Without our domestication though (and our decimation of their natural home), dogs would be happier in the wild in their packs.
We justify our structures of school by saying things like “children crave structure and routine.” This becomes true over the years. This is only true because our schools have trained and indoctrinated children to need the structure and routine in order to do what school demands of them. Without that training and indoctrination though, children would be much happier self-organizing and learning what they choose and how they choose for the purposes that they choose.
(Don’t worry, adults. Just as we still need our elders, so still will the children need theirs.)