I'd imagine those issues have the support of Administrators. Bucking the Administration and challenging "the system" is likely not too popular. How much can one change the system by being fired?
Administrators and teachers have separate unions, at least in CA. It's kept that way for just the reason you described. Administrators can't be present at any teacher's union meetings, either.
Teachers with tenure can speak out as much as they like without fear of being fired. There are worse things that can happen to you than being fired. Admins who still have it in for a teacher they don't like can still try to make things rough on them, but it would be difficult if the teacher were actually a part of the union, since an Admin really does not want to have a file full of grievances filed against him/her.
One reason why teachers in LAUSD threatened to strike three years ago was because the state had sent them earmarked money for a $10,000 raise for each teacher. (That would push starting pay for a credentialed teacher up to $36,000 at the time, in an area where you need at least $300,000 to buy a 1200 sq. foot house, and you will still be commuting for an hour, so it would still not exactly be living high on the hog.) The state did this in an effort to encourage emergency credentialed teachers to get their credentials, and to try to retain teachers, since over half quit within the first 5 years.
Anyway, the teachers were told that year that there would be no raises or step increases due to lack of funds. The district literally had already spent the money on redecorating the enormous downtown offices. Complete with mahogany desks for anyone in the brass. THAT is why the teachers were so upset in that case, and I don't blame them.
One?
If most teachers are good people who want what is best for kids then there would be thousands, millions? Not one. Hardly a thing administrators could do.