This is an interesting take that I had not expected to read when going to this comments section, but you're absolutely right. But this applies to almost everything. Every time I read a report of a sanctioned (non-criminal) or poorly evaluated public school teacher, I think of my friends who are teachers: how they've had to juggle everything in their personal lives in addition to the emotional and physical drain that comes from being passionate about teaching children, especially if the school's administration is terrible.
After that, it's harder to judge the teacher in question, knowing that there could've been any number of strains that led to a troublesome incident or poor performance report.
It doesn't, but think about it from their perspective. Do you base performance on number of A's given? On scoring on standardized tests that only show how well you taught students to take tests? Where do you include "opening a student's eyes to the power of reason and science" or "planting a seed of a deep love for literature" or even just "being a person a student wants to be like"?
It isn't much different than how've question of how to evaluate coders. Any mechanism that can be easily proscribed can be easily gamed or is meaningless. Any mechanism that truly measures worth is extremely complex, doesn't scale, and may have issues with labor laws.
I wouldn't want that crap legislated by state legislatures, either.
After that, it's harder to judge the teacher in question, knowing that there could've been any number of strains that led to a troublesome incident or poor performance report.