Because that all fits the anti-union PR. The mere presence of the union suddenly cuts down on the shittiness of the administration. Teachers stop getting jerk

Because that all fits the anti-union PR. The mere presence of the union suddenly cuts down on the shittiness of the administration. Teachers stop getting jerked between classes and classrooms. Teachers can't get forced into doing extracurricular activities. etc. The union also pays the legal bills when teachers get sued by idiotic parents because they had the temerity to teach evolutionary theory in a science class. And, as I have pointed out previously, a lot of the "can't get rid of teachers" is due to the fact that the administration simply won't file the paperwork to get a teacher fired. You see, if you file the paperwork, that becomes a record and can wind up public information. That record is likely to come up when the administrator is trying to get a promotion or a new job. So, rather than creating a paper trail to fire the teacher, these administrators would rather transfer teachers to a "rubber room" and bury the problem so that it won't haunt the administrator's promotions in the future.