As large school districts defy Florida's ban on strict mask mandates, worries that rapidly spreading infections could force them to close classrooms are no longer theoretical. Thousands of schoolchildren are already being sent home, only days after their school year began.

"Children particularly those too young to get vaccinated against Covid-19 are really good at transmitting the coronavirus," AP quotes Dr J. Stacey Klutts, a special assistant to the national director of pathology and lab medicine for the entire Veterans Affairs system, as saying.

Klutts said the highly contagious Delta variant makes it absolutely necessary to wear masks indoors and avoid large group gatherings, so if unprotected students sit for hours in classrooms every day, it could rapidly spread infection in the community at large.

Florida reported 23,335 new Covid-19 infections on Tuesday, the US Centers for Disease Control and Prevention said.