I retired 3 years ago, but the last 10 years were in a referral unit (excluded kids) not mainstream.
I started in 74.

Erosion of respect and discipline made the job steadily harder and less rewarding, but teachers were largely responsible for that by bringing in liberal regimes.
It used to be one adult and a blackboard with a large class.
Not possible now.

Ex-teachers who become administrators are another problem.
They are very good at thinking up extra things for teachers to do that benefit the students.
Actually anyone could do that, but they never suggested anything teachers could stop doing to make time for all the new things.

Now most new teachers quit after a couple of years.