Let's simulate testing in schools. Let's assume better performance of tests than research: https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm
sensitivity to be at least 90% -> 0.9 = P / (P + FN) specificity to be at least 99.5% -> 0.995 = N / (N + FP)
There are on average 25 pupils in each class. If any of them has positive test result, all of them are quarantined for a week.
Incidency of real positives should be around 2.5% (in current state). There are also, let's say, around 4% absenteers for another reason. There are about 1.5M pupils in schools.
How many classes are going to be quarantined and how many of them due to false positives only?