The funny thing about school is that almost no adults would be willing to be subjected to it. Confined to a building every day for the best years of your life, required to study what the government decides should fill your head, and a persistent risk of being beaten up. Delightful.
Ultimately the main reason that schools exist in their present form is because they are economically useful. Parents need somewhere to park their kids, while they go to work. As a child I could never understand why adults would inflict the barbarism of school on their own children, were they not aware? As an adult it all makes a lot more sense.