From the Maryville Daily Times:

A Maryville third grader tested positive for COVID-19 after a Monday, June 22, trip to Springbrook Pool with the Foothills Elementary School Adventure Club.

The student passed a Monday morning temperature check at the extended care program but was sent home when the midday check registered more than 100.4 degrees Fahrenheit, according to Maryville City Schools Director Mike Winstead.
...
“We did what our management plan and the Health Department says we should do,” Winstead said. The Health Department will be responsible for other contact tracing.
...
“When school reopens and we have 5,000 kids and 900 employees and all the interactions going on, having a positive case is inevitable,” Winstead said. “The key is just controlling interactions and minimizing the impact of a positive case.”

About a dozen other Adventure Club attendees will have to submit to a 14 day quarantine.