To not have your child vaccinated is antisocial. If they are going to a public school vaccination should be required for entry. If the private schools want to enforce other rules that could be their prerogative. There have to be consequences for antisocial behaviour. Required vaccination for entry to public school is the norm in much of the industrialised world. That is how pandemics have been prevented, smallpox was eradicated, polio was stopped, diphtheria is now essentially unknown, and measles was rare until the advent of international travel and folks who choose not to vaccinate their children.