At least four teachers have died of coronavirus-related causes since the beginning of the school year—an ominous sign of what’s to come as students return to classrooms across the country. Demetria Bannister, 28, a teacher at Windsor Elementary School in Columbia, South Carolina, died on Monday, just three days after being diagnosed with COVID-19. Her parents “wish to remind others about the seriousness of this disease,” a school district spokesperson said in a news release, according to The State. She was described as an avid singer who “loved her students and never missed an opportunity to advocate for students and public education.”

Two teachers died in Mississippi and AshLee DeMarinis, 34, a teacher at John Evans Middle School in Potosi, Missouri, died on Sunday. The coronavirus had already devastated schools before the summer break. In New York alone, 75 Department of Education employees died from COVID-19, including 31 teachers. The American Federation of Teachers said 210 of its members have died of the virus.