At least nine of the 20 largest US school districts are making masks optional for students Los Angeles Times via Getty Imag Carolyn Cole/Los Angeles Times/Getty Images Students wearing masks head to lunch break during summer school at Hooper Avenue Elementary School in Los Angeles on June 23. By Elizabeth Stuart, CNN As the new school year quickly approaches, at least nine of the 20 largest school districts in the US are making masks optional for students in school while another nine are requiring masks. Two districts remain undecided with just weeks left until schools plan to open their doors. With varying rules for indoors and outdoors, and with vaccines only available to children older than 12, back-to-school is not as clear cut as parents might have hoped it would be. And whatever the rules are today, the districts are making it clear that they will continue to change their guidance according to local public health conditions even after the school year starts.