NEW YORK (AP) — Teachers and other school staff members are supposed to be vaccinated against COVID-19 when the bell rings Monday morning for New York City’s sprawling school system. Mayor Bill de Blasio has warned that unvaccinated school staffers will not be allowed to work Monday. De Blasio said 90% of Department of Education employees had received at least one vaccine dose, including 93% of teachers, as of Friday. New York City’s school district is one of the first in the nation to require all school employees to be inoculated against the coronavirus. A similar mandate is set to go into effect in Los Angeles on Oct. 15.