Teachers in Los Angeles County will be required to wear high-grade masks while in class, while staff and students must wear masks outdoors in crowded spaces under new rules. The rule, which applies to both public and private schools in the county, was implemented as students return from their winter break, according to updated guidance from the Los Angeles County Public Health Department. “During this surge, given the spread of a more infectious strain of the virus, lapses can lead to explosive transmission,” Public Health Director Barbara Ferrer wrote in a news release Sunday. “Well-fitting and high-quality masks are an essential layer of protection when people are in close contact with others, especially when indoors or in outdoor crowded spaces where distancing is not possible.” The mask guidance was updated after the surge in infections and was blamed on the spread of both the Omicron and Delta variants. Los Angeles County …