In New York City, parents do not have the right to send their unvaccinated kids to school if another student has a vaccine-preventable illness.

That's according to a Brooklyn Federal District Court judge, who ruled earlier this month that a parent's constitutional right to freely exercise their religion does not always make their children exempt from vaccination requirements.

a parent's right to exercise their religion does not always make their children exempt from vaccination requirements

New York City schools require all students to get a series of basic vaccinations in order to attend classes. But in New York State — along with several other states — laws say that parents can opt out of these requirements for religious reasons.

When three families in New York City recently tried to do so, their children were barred from attending school, leading them to file suit against the city. Citing a 1905 Supreme Court case — in which the court ruled that Massachusetts was permitted to fine a man $5 for refusing a smallpox vaccine — Judge William Kuntz ruled that the court had "strongly suggested that religious objectors are not constitutionally exempt from vaccinations."

Of course, the plaintiffs plan to appeal the ruling, and this is just one of several similar suits filed across the country in recent years. Given that 48 states allow religious exemptions for vaccine requirements, the ruling will certainly be tested at higher levels before it becomes a real policy.

All this comes as increasing numbers of parents around the country are refusing vaccines, leading to outbreaks of a number of diseases that could have easily been prevented. Earlier this spring, during a measles outbreak in New York, the unvaccinated sibling of a home-schooled child who'd been infected was barred from attending public school. That sibling ultimately contracted the disease, and keeping him home prevented it from spreading further.

For a great explanation of the anti-vaccination crisis, watch this two-minute video:

Correction: This story originally stated the decision was made on Sunday, not earlier this month. It also stated all three families opted out of the vaccine requirements, when in fact two did, and one family tried to but had their request rejected.