Let me provide full disclosure and divulge I've been a Teamster. Many, all-to-many times I felt that my union dues were merely going to cover the cost of protecting lazy, good for nothing, POS who should be kicked out on their ass. I showed up every day, got excellent reviews, did my job without fail and for all intents, didn't need union representation. Now my pay at the time was about 30-40% more than at a non union shop. It was that way because of union representation. So, what those 30% of teachers did essentially is say, well, we got what we got because of the union and now, well, piss off. The other end of the bargaining table loves this. Why? because it provides the context and framework to slowly, ever-so-slowly chip away at all the rights, benefits, salaries that the Union got them, which could have only be gotten through solidarity in collective bargaining.
Again, this isn't where the main ire I have lies, if people are too stupid to realize this is nothing but a "divide and conquer" strategy, they deserve what they get. God don't save stupid.