US states and parents are divided over whether masks should be mandatory for students returning to school classrooms.
The US Centers for Disease Control and Prevention earlier recommended that all students and teachers from elementary through high school levels should wear masks indoors. The move aimed to limit the spread of the highly transmissible Delta variant of the coronavirus.
States including New York and California, which are considered relatively liberal and headed by Democratic governors, have introduced mask mandates at schools.
Children at many schools across Los Angeles, California, wore masks when the new term began in the middle of August.
Views that mask-wearing should be a personal choice are strong in Republican states. Parents in Broward County in the state of Florida held a rally last month, protesting against compulsory mask requirements at schools.
Florida Governor Ron DeSantis, a Republican, has publicly opposed mandatory masks in schools. He issued a ban on mask mandates, threatening to withhold funding if schools failed to comply. A state judge ruled the ban was unconstitutional on Friday. However, US media reported on Tuesday that the Florida Department of Education had withheld funding from local school districts that defied the ban.
The governors of Texas and Arizona have also taken steps to oppose mask mandates.
Public health experts have voiced concerns that politicizing the issue of wearing masks could potentially impact the health of children.