The most important thing school taught me is how to cope with pressure.
Not how to pay taxes and not how to be successful.
But how to interact with others, argue and learn. How to make a compromise and widen my horizon.
I usually hate when people say „school teaches you how to learn". It is true though, instead of teaching you stuff that is useful in society, it teaches you how and what you want to learn. Preparing you for any way you want to go.
Its method is questionable though. Learning through a grading system is not really how the world should work.
A mix of both would probably be recommendable: learning useful stuff about our society while learning how to learn.
School taught me what to improve in our society and how to stand up for what I believe. I believe in the changes I want to make now, yet will I be able to get far with them in the real world, school is keeping us from?