Pediatrics, a peer reviewed journal affiliated with the American Academy of Pediatrics has accepted for publication a study that finds that school districts that practiced universal masking had a 72% reduction in in-school transmission vs districts that utilized partial masking i.e. optional, optional masking prior to universal masking or only masking at certain grade levels.
This large study spanned 61 k-12 school districts in 9 states in the United States and had a study population of nearly 1.3 million students and staff members.
This study examined whether cases that originated outside of schools in the community were being transmitted between close contacts within the schools. They found that partial masking districts had 3.6 times the number of secondary transmission cases as those that universally masked.
The findings of this study support other studies that have shown school masking effectiveness on decreased case transmission but also support reverting back to masking as a mitigation measure if community case levels are high; masks were shown to be very effective in reducing in school transmission allowing children to remain in school for in person instruction.