I've been teaching for nearly 20 years and the majority of teachers I've met or worked with work very hard. Yes, I've known some who should be in a different job, but they are the minority. Most teachers are there much longer than the adminstrators.
Yes, sometimes teachers don't want to add to their work load without being paid for it. I don't think that makes them unusual or unreasonable. Two years ago this state cut a program that paid teachers for doing extra work. This program paid for things the teacher did beyond their job description. The first time the legislatiure tried to cut it at the end of the school year. This would have denied payment to the teachers after they had done the work. We avoided that but they cut it for the next school year. This meant a pay cut of up to $5,000. Now I do know that some teachers have stopped doing some of the things funded by this program, but most of the work is still being done. Expecting to paid for the work you do doesn't make one a bad teacher.
Finally, for all the anti-union out there. Last in first out is common in most schools regardless of the union. I've said this so many times but people don't seem to believe it. Not all teachers are in a union.