In the old days, before collective bargaining, teachers were often subjected to the rule of tyrannical principals and superintendents.
Teachers were fired because they were pregnant.
Principals demanded teachers take certain duties, or risk losing their jobs.
If teachers have no rights on the job, anything can happen. Before unions, the right to file grievances, and contract agreements between unions and school boards, teachers were fired for a variety of reasons.
Here is a selection of news articles about teachers being fired for a variety of incomprehensible reasons:
1957: Teacher fired for being a member of the NAACP. (published May 28, 1957, The Afro-American: Google Archive)
1961: Teacher fired for assigning the book, 1984, to her class. (published October 22, 1961, St. Joseph News-Press: Google Archive)
1962: School board ordered to rehire teacher who was fired for rejecting to an assignment to chaperone a student bowling club for the entire school year. (published April 18, 1962, Gettysburg Times: Google Archive)
1969: Teacher fired "...because he wouldn't shave off his beard..." (published January 31, 1969, Spokane Daily Chronicle: Google Archive)
1976: Teacher fired "...for taking days off on religious holidays..." (published July 14, 1976, Spokane Daily Chronicle: Google Archive)
1977: Unwed teacher was fired after giving birth, later won her job back. (published July 15, 1977, Ocala Star-Banner: Google Archive)
1975: Four Ohio teachers fired for having mustaches. (published November 14, 1975, Daily Sentinel: Google Archive)
2004: Teacher fired because "..he refused a parent's request to change a student's grade..." (published June 2, 2004, City Beat)
If you haven't taken a look at the legislation proposal called SB 5, you might want to visit the link for SB 5.