Here are some references from the CDC website for higher education. The recommended focus of testing is on suspected cases or those who have been in contact with confirmed cases. In short, they are not recommending individual testing for persons who do not meet these criteria. Some schools are doing random sub-set sample testing. However, this requires statistical consideration to be robust (e.g. consideration to population size of students, faculty and staff, frequency of movement between the institution and the community).
In fact, even when there are higher rates of transmission in the community, CDC is not recommending testing in schools.
Some countries do school testing as part of a surveillance system. This is the current strategy for NYC – to enable monitoring the extent to which schools contribute to transmission. According to the New York Times, “The city is currently planning to test a random sample of 10 to 20 percent of people, including students and adults, in each city school once a month starting next week.” Surveillance is the practice of testing a random sampling of a certain percentage of a specific population to monitor for increasing or decreasing prevalence and determining the population effect from community interventions such as social distancing. Note that this strategy is NOT about finding cases – it is about monitoring trends.
Also very important, there is still no evidence to suggest that schools are a major driver of transmission. According to the WHO and the most recent peer review literature “few outbreaks involving children or schools have been reported. However, the small number of outbreaks reported among teaching or associated staff to date suggests that spread of COVID-19 within educational settings may be limited.“
The CDC guideline for higher education has the following guidance on testing for higher education: IHEs might test students, faculty, or staff for purposes of surveillance, diagnosis, screening, or in the context of an outbreak. Individuals should be considered for and offered testing if they:
Show signs or symptoms consistent with COVID-19 (diagnostic)
Have a recent known or suspected exposure to a person with laboratory-confirmed COVID-19 (diagnostic)
Have been asked or referred to get testing by their healthcare provider or health department (diagnostic)
Are part of a cohort for whom testing is recommended (in the context of an outbreak)
Are attending an IHE that requires entry screening (entry testing as part of screening)
Are in a community where public health officials are recommending expanded testing on a voluntary basis including testing of a sample of asymptomatic individuals, especially in areas of moderate to high community transmission (screening)
Volunteer to be tested in order to monitor occurrence of cases and positivity rate (surveillance)
It is not recommended to retest previously positive asymptomatic individuals within 3 months of a positive test. Data currently suggest that some individuals test persistently positive due to residual virus material but are unlikely to be infectious.