Generally a good school has a great Principal. In my wife's teaching career we have seen a good Principal replaced by a hack. Almost immediately the quality of education suffers. Good Principals hire only good people and take good diciplinary steps and have good policies.
Some times it also maybe best to stay out of the way of the administration -- in your case this could be a learning experience for you child. You have to let your kid know that in the real world they will work for jerks and be surrounded by incompetents.
It is pretty easy to tell the quality of the school by looking a the statistics -- like SAT scores, absenteeism, drop-out rate and others. Most times the numbers are scrubbed or not shown.
I tell my son that not everything in life is fair, he understands this. It's the parents who are upset. The teacher and the Vice Principle have lied and withheld information for their own benefit. The parents have met with the administration individually and we have been told different versions about what happened and why the punishment was issued.