My mom is a teacher and works harder than many others. There are many that simply know the union is there to protect them and do as little as.possible. One of my moms best friends is a speech therapist in the school district and openly brags about how she doesn't care and that the district can't do anything to her. She makes about $90k a year.
Therein lies the problem. Master's degrees and PhD's moved into administrative or "specialist" positions where they make lots of money but make little or no difference. The teachers who actually make a difference in the classroom are often under-paid and misrepresented by unions who only protect the lazy zealots and the over-educated administrators/specialists.
It's a pitiful sight, and I can scarcely fault federal regulators for overstepping their constitutional authority to fix it.