Just catching up...
It's obvious that there is some work going on around looking at the risk to teachers which, knowing the way the govt works, means that they have been spooked. However, it is also obvious that the data are being manipulated to suit the "teachers are safe" narrative that the govt has decided on. I understand the position of the teaching unions and definitely believe schools should shut this time, but I wish that they hadn't been so vocal because politically they have shot themselves in the foot as a Tory PM is never going to accept the request of a union. And fuck knows what Kier Starmer is doing.
Another thing that you boffins have probably already covered on these threads is sensitivity and specificity. No test will be 100% correct but the most we can hope for is to miss as few cases/have as few false positives as possible. However, sensitivity of a test is dependent on the population in which you are using it, who is doing the test and the concentration at which you judge that test to be positive. I admit I haven't looked into what constitutes this test, but anything involving DNA and antibodies in is affected by temperature and a hundred other things. If anyone is interested in further reading about tests and sensitivity google articles for the faecal immunochemical test which is used in asymptomatic patients (for sceeening), patients at low risk of having colorectal cancer and also patients who are being referred on a 2WW pathway for suspected colorectal cancer.