have an arsenal of methods to get rid of unwanted teachers, and no, they don't have to be "bad" ones at all to get sacked.
"Fired" or, to use the correct bureaucratic term, "dismissed," in public ed, simply means some idiot principal has put in a "recommendation for dismissal" which the post-probationary (misnamed "tenured" teacher decides to appeal the dismissal to the superintendent/board and ultimately the hearing officer or panel or school board, and in some 3/4ths of the cases, they "lose" the case. Then, if they can get an outside attorney if they didn't have one already to take the case, a near impossibility, they go through the civil court system since the law restricts appeals of administrative law "cases." Administrative law, which termination hearings are part of, is a complete and total farce, manipulated with abandon by school districts. Things that would get lawyers and others disbarred or thrown in prison for in civil or criminal cases are allowed in these fake tribunals.
Even if you "win" or are "reinstated," you will have a target on your back for the rest of your career. Once you piss off public school administrators, you are cooked.
However, the overwhelming majority of teachers faced with "termination" either retire early or they resign in lieu of a dismissal, usually the latter in some mistaken belief that it will help improve their chances of getting work elsewhere. It doesn't, for it is seen by other school districts as an admission of guilt regardless if the teacher is guilty. After all, why wouldn't you appeal a dismissal since it doesn't cost you anything unless you were guilty?
And of course probationary teachers are fired all the time; school districts, however, don't call them being "fired" but instead are called "non-renewed" or "non-re-elected" in cases where the situation is NOT a layoff.