I do not understand why anyone is a murderer in this case. Even if an unvaccinated classmate is in your child’s class it doesn’t mean that he is the cause for the disease. By this logic your child should never leave the house because he may catch a disease from someone in the street.
As far as the vaccines only working 90% of the times you have to have faith, when you drive your car do you stop at every intersection or do you rely on the fact that most people obey traffic law and don’t run red lights and stop signs?
Everybody should be entitled to a yeshiva education no matter what their vaccination status is.