The deaths in Broward County come as a fierce debate rages across the US over what virus protocols should exist in schools when the academic year begins.
Florida's Republican governor has threatened to withhold pay from school leaders who require masks for pupils.
The highly contagious Delta variant is spreading across a majority of the US.
Three teachers and a teaching assistant died between Tuesday and Wednesday in Broward County - which is just north of the Miami-Dade area. Their names were not released.
