Heavily agree with @tangyerik on this one. If you don’t vaccinate your kids, you shouldn’t be allowed to send them to public schools.
Mumps can cause meningitis (about 1 in 10 cases) and deafness. This isn’t the same as someone just showing up to work with a cold and getting the whole office sick. This decision to allow a disease to spread could have far reaching consequences for hundreds of other people. If you don’t want your kids to be vaccinated, then don’t expose others to the diseases they will more than likely contract.