An interesting book on this topic:
Summerhill: A Radical Approach to Child Rearing
Also:
A guy tought pre-school kids how to solve linear equations.
But he was an outsider so butthurt academics buried his research even though it was proven to be better:
Direct Learning, Sigfried Engelmann
https://shallteach.wordpress.com/2020/05/18/di-an-introducti...
