> for the narrow purpose of attending public school

That doesn't seem all that narrow; 90% of the population goes through the public school system. (Side note: I'm in NY, and our vaccination mandate covers private/religious schools, too.)

> well-tested and -understood vaccines

Like the COVID vaccines, sweet.

> illnesses far more threatening to them than Covid

Missed the chickenpox one, did you? Killed ~100/year before the vaccines. COVID's killed 805 children in the US so far, per https://covid.cdc.gov/covid-data-tracker/#demographics.