Students attend an in-person class in a school in Los Angeles, California, the United States, on April 13, 2021. Since the outbreak of the COVID-19 pandemic for the first time in more than a year, some Los Angeles schools reopened for in-person classes on Tuesday. Safety standards and mandatory COVID-19 testing of students were in place, but many parents still opted to keep their kids learning from home. (Xinhua)

Students attend an in-person class in a school in Los Angeles, California, the United States, on April 13, 2021. Since the outbreak of the COVID-19 pandemic for the first time in more than a year, some Los Angeles schools reopened for in-person classes on Tuesday. Safety standards and mandatory COVID-19 testing of students were in place, but many parents still opted to keep their kids learning from home. (Xinhua)