So those who can, teach.
But, who chooses what the learner needs to know?
As I ponder my own "best" teachers, I find they were the ones who taught me something of value later in life. A modern quote says there would be no other professions if it weren't for teachers. After all, they teach the doctors, lawyers and Indian chiefs. Or do they? Aren't our parents our first teachers? Shouldn't they be? Teachers have a huge, humongous, astronomical amount of influence over our children.
Perhaps too many parents have given up their right (duty) as their children's first teachers. By default, they've simply handed that privilege over to others in school systems across the country.
It doesn't take much effort (historically) to find a people who can tell you what happens when others take control of what your children learn. It wasn't their choice to sacrifice their children. But they can tell you the result.