How is it in the public interest for a teacher to be fired for giving a failing grade to the school administrator's, mayor's, or influential businessman's son/d

How is it in the public interest for a teacher to be fired for giving a failing grade to the school administrator's, mayor's, or influential businessman's son/daughter/nephew/niece who goofed off in class, didn't do their homework, failed the tests, etc.? If you have no objective criteria for what constitutes a firing offense, you will have good teachers being fired for political reasons rather than educationally valid ones. If you eliminate the protections of tenure, you also destroy the teacher's ability to apply their professional judgment on educational matters in a uniform manner.