IS the child simply missing the MMR vaccines (measles, mumps, and rubella)? If you've already received this vaccine AND the bosoter when you were a child, you should be OK. For more info, see the CDC vaccine website.

Is that not mandatory for vaccine updates before a student can be enrolled?

I would talk to the Principal and have it enforced.

If it doesn't put you or your other students in harms way, it certainly puts that kid in harms way, and that;s already too risky i would think.

The idea is that the other children have been vaccinated and should "technically" not be susceptible to illness by virtue of being exposed to the illness in a small dose. That's what a vaccine is. People who choose to refuse vaccination for their children do so because they feel that the immune system is either:

a. strong enough to fight off illness itself OR
b. will develop immunity to an illness after the body has processed and gotten rid of it