Edward Campbell, a microbiologist at Loyola University, started SafeGuard after learning about a virus test developed by researchers at the University of Wisconsin-Madison. SafeGuard serves approximately 30 school districts and runs approximately 30,000 tests per week, at $ 11 per test, said Dr. Campbell.

Updated

March 30, 2021, 9:52 a.m. ET

New Trier has also registered, but the introduction of the test did not go smoothly. Minds flared at school council meetings, with some advocating the opening of the school, citing the damage being done to the mental health of students. Others questioned the urge to stay open even though Covid-19 rates skyrocketed in Illinois.

Some parents made T-shirts, set up a website, and held a rally in support of the reopening. A group of students countered with an online rally. The testing program upset the community, turning administration against teachers, students against administration, parents against teachers, and parents against parents.

“Many children do not even want to go to school because, in addition to the risk of Covid, it is not pleasant to be in school,” said Eva Roytburg, 18, a senior citizen in New Trier.

Nevertheless, the school pushed ahead with the tests. Dr. Campbell’s laboratory analyzed saliva samples from students from New Trier and provided the results in a table in which students who required a confirmatory test by a certified laboratory were marked.

Although SafeGuard technically did not provide a diagnosis, the implication was clear – after quick testing, it was assumed that some students were infected, and she and her siblings were sent home.

The company and the school refer to this as surveillance. While surveillance programs can measure the prevalence of a disease or pathogen at the population level – for example, that 10 in 1,000 high school students are infected – they do not provide results for individuals.