AUSTIN (KXAN) — An analysis of some of Central Texas’ largest school districts shows districts without mask mandates have significantly more cases of COVID-19 within the student body and staff than those that implemented mask mandates at the start of the school year.

Currently, 11 of the 20 districts analyzed require masks.

Of those districts, the three with the highest percentage of students and staff cases do not require masks.

Those districts are Burnet, Liberty Hill, and Lago Vista ISD.

Lago Vista has the highest number of cases on a per capita basis, with more than one in every 13 students and staff members infected this school year.

The surge caused district leaders to shut down the high school for the rest of the week. Students there will instead learn online until they can return to campus Monday.

Dr. Donald Murphey, an Austin pediatric infectious disease expert and member of the TMA COVID-19 Task Force, said this discrepancy isn’t a coincidence.

“COVID is spread mostly person to person, mostly in fairly close contact, by talking speaking, by droplets and masks interrupt that transmission,” Murphey said.

Only one of the 10 districts with the highest case numbers, Elgin ISD, required masks at the start of the school year.

The four districts with the lowest percentage of cases (Austin, Round Rock, Manor, and San Marcos) all required masks before the school year started.

Austin ISD leads the way with the lowest number of COVID-19 cases per student and staff member, with roughly one in every 159 getting sick.

However, the raw numbers don’t tell the whole story.

“It is a really complex topic,” Murphey said. “I think the start of it is how much COVID is there in the community? Then if you look at the number of kids in the school, you’re going to have the same positivity rate in kids showing up to school as there is out in the community most likely. Then the next question is, is it spreading in the school? So masks are the best way to stop it from spreading in school.”