This fall, as many schools across the country are planning to reopen for full in-person learning, parents and educators are bracing for the third straight school year to be disrupted by COVID-19.

And yet, according to one survey by the Center for Reinventing Public Education, of the 100 biggest urban school districts in the nation, only 13 have some requirement that teachers be vaccinated. Just seven of those—Chicago, Denver, D.C, Portland, Seattle, Los Angeles, and as of Monday, New York City—have made the vaccine requirement universal for all school staff. Which means that the vast majority of biggest school districts in the country are allowing at least some unvaccinated teachers into the classroom, even if they have other safety requirements, like testing or masking.