What would happen with a professor who flunked a much higher proportion of his black students than white?
What would people here say if a professor flunked a much higher proportion of his white students than black or Hispanic? Or flunked more Asian students than anyone else?
They might claim bias. Well, the other groups might do the same when it happens the other way.
For STEM courses, no one really has a good argument. You either pass the tests or you don’t.
OTOH, for courses heavy in writing, professors sometimes show bias, especially on politics. If you agree with them, you might get a better grade.
But, most students drop their courses when they’re not doing well. They don’t get an F if the course never shows up on their transcript.