In my district in Texas we have an “unwritten policy” that says that a teacher shall not have higher than a 20% failure rate. It does not matter if 25% of the student don’t show up regularly, it’s the teacher’s fault. It doesn’t matter if they skip every test given in class and then refuse to make them up, it’s the teacher’s fault.
If the failure rate is above 20% percent then the teacher has to do a mountain of paperwork to justify the failing grade. If the problem persists, then the teacher will be places under a “corrective action” plan.