As school districts across the country look to begin reopening in the fall, one incident seems to be indicative as to why it will be increasingly difficult to operate the United States' 13,000 school districts amid the COVID-19 pandemic.

More than 40 San Francisco Bay Area school principals have been advised to self-isolate after being exposed to coronavirus during an in-person meeting, where the topic of discussion was how to reopen schools safely. The San Francisco Chronicle reports that the exposure took place at an in-person meeting on June 19; a pre-symptomatic attendee tested positive for the virus a few days later.

During an online meeting with the school board last week, District Superintendent Stella Kemp verified the exposure. “Given the complexity required in the development of our reopening plan, some of our staff meetings are taking place in person,” Kemp said, per the outlet. “Of course those meetings are being conducted under the strict guidelines provided to us by the Santa Clara County Public Health Department.”

Some on the school board wondered why Kemp chose to have an in-person meeting when county guidance says indoor meetings should include 10 people or less. Kemp maintained that the meeting was crucial, clarifying that attendees were tested and from what she knows, no one tested positive.

Conversely, the county public health order doesn’t provide specifications on how many people can attend a meeting, but does say, “Only those employees performing job duties that they cannot feasibly perform from home may come to a business’s facility to work.”

This week, the American Academy of Pediatrics—which represents 67,000 pediatricians—also said that students should return to classrooms as soon as possible, the biggest endorsement we’ve seen yet for reopening schools, according to U.S. News. The group surmised that the academic, physical, and mental positives to reopening exceed the dangers, particularly since evidence shows that children are more likely to show milder symptoms when they are infected. Still, the virus can spread rapidly among adult educators and administrators, many of whom are older and thus, more at risk.