It's their private fiefdom for the purpose of jobs and prestige (educating the children comes in a distant third, if it's even considered at all.)
Can't let somebody in who might upset the apple cart by actually teaching something and getting the children all excited about learning. The deadwood timeserving teachers might actually have to WORK . . . .
And yes, yes, I'm sure there are SOME good teachers out there in the public school system. But I haven't met any of them. All the good teachers around here take LESS pay to teach in the private schools, where they are actually allowed to teach and have students who actually want to learn.
As a retired HS teacher, I can vouch for those required Education courses not being worth a bucket of warm spit. I sat through them ruminating on whether the course material made the professors so mind-numbingly dull or whether they were dull to start with and gravitated to such course material.
Many very good private schools don't have "education school" teachers on their staff.