Bad management kills passion instantaneously. The best teacher, faced with administration which will constantly kowtow to parents and refuse to discipline bad students, will lose their passion rapidly.

I had a friend who left teaching because of this sort of thing. They had a terrible experience as a student teacher and decided to work a job that paid less money.

The policies didn't just crush the teachers. Many of the students didn't care at all. There were behavioral problems, of course. One major issue he saw was that the school just pushed kids through the grades. There was a policy of an automatic minimum grade of 50% if the kid just put their name on the test... and they still at least one kid who would refuse to put their name on the paper!

Another friend of mine also went into teaching, but they refuse to work for public schools because of the bureaucracy, even though that sometimes means taking a paycut.

"there are those in teaching who find it that they dislike it but still trudge along because nice benefits (not talking about US), much to the detriment of their students."

This definitely happens in the US too. There have been documentaries made which include things like teachers just reading the news or a book whole letting the class do whatever it wants. Then the lawsuits and fight over tenure when the administration tried to fire them. Maybe the pay and benefits aren't great in many areas, but they're better than nothing, especially considering if you can do other things during work hours.

Even in districts where there is a union issue with firing, you could not easily find good replacements anyways. The pool of passionate teachers willing to take these roles is a small percentage of the total jobs, and they tend to self select into good higher paying districts with better behaved students.