Well, at least one well-known outfit is finally recognizing it for the scandal it is.
Bullying is horrible enough, but administrators do it because they can. It all depends on the district and how ethical their legal departments are.
If they are like Washoe County School District, they force teachers out in order to force a lawsuit or a severance package deal. They are of the mentality that since it isn't their money, they can waste taxpayer money any way they please.
There are some school districts that do follow the law, albeit not too many, but that is only with the knowledge they are supposed to be wise stewards of taxpayer money.
A termination or forced resignation/retirement is bad enough, but the financial devastation, which can last the remainder of a dumped teacher's life, is much worse.
You never, ever heal from the experience.
The biggest reasons bullying and other tactics by administrators against teachers go on are because administrators are not closely supervised, and they are backed to the hilt by school districts.