Experience is the best teacher, and the purpose of school is to prevent experience.
If school attendance were voluntary, schools would have to reform themselves to meet students needs, because if students could leave on a whim, schools would suddenly have to prove their worth. Because kids grow up in an oppressive society, it's predictable that when they leave the controlled world of childhood, they vote for politicians who promise security instead of freedom. Few adults understand freedom and individual rights because we're taught about the Declaration of Independence, The Constitution, and the Bill of Rights in school, the most authoritarian environment in America next to prisons. Kids learn early on that even in a free country you are mandated to sit in cramped desks, read, write, and listen against your will. If you think for yourself in school, you get bad grades, and that's why America doesn't notice the government stripping away our rights.