Due process should be carried out in a way independent of involved parties; ie, it doesn't matter if the union strikes, cases involving abuse of students or other similar misconduct should be heard by a court or other legal body independent of the school system.

As in, the school should not have the authority to fire or punish teachers inside of its structure, and needs to be outside of the influence of both the schools and the unions to maintain fairness and safety.

If you did the crime, you do the time, no matter if it even results in the union striking for the entirety of your prison sentence.