The rule should be, quite simply, “No admission to a public school (or to the US) without immunizations.” Period.
There’s always home schooling, permissive private schools, or online education for those who can’t or won’t get immunized.
The unimmunized are walking, talking disease vectors that should not be allowed to circulate freely in our society any more than the diseases themselves. Current and recent measles, mumps, and chicken pox outbreaks should never have happened. Nor the TB scare in Aurora, Colorado.
But for the irresponsible, selfish, and/or ignorant few, these diseases could and should have been completely eradicated. Yet the unimmunized continue to put us — especially children, pregnant women, and the elderly — at risk. It’s unacceptable and entirely preventable.
In short, there ought to be a law.