The Government has been very poor in spelling out what 'mass testing' in secondary schools means, and the mainstream media has not been clarifying the issue. I am repeatedly seeing misconceptions on MN based on this poor messaging.
The guidance released (obviously dates will now change to an extent) is here:
assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/947799/schools_and_colleges_testing_handbook.pdf
Leaving aside arguments about practicality (it is interesting that they have removed an earlier version of the guidance in terms of numbers of people required, but even this version says that a secondary school of 1000 will need 13 members of staff to administer testing), let us think about the TWO SEPARATE types of testing and whether they make schools and their communities safer or less safe.
The initial testing is of two separate tests 3-5 days apart (a total of 6.8 million tests would be needed for this phase). This would, if done successfully, improve the safety of schools temporarily, by identifying some cases that would not otherwise have been detected, and requiring them to isolate.
Of course, within a short time, as students go about their daily lives and potentially pick up infections but are not tested again, this marginal improvement in safety is not maintained.
The second test of testing is not, as a rational person might assume, an ongoing randomised testing programme that could pick up outbreaks within schools quickly and remove infected individuals from circulation.
Instead, it replaces the current isolation of close contacts of someone who tests positive with 'serial testing' over a period of 7 days (in effect, 5 tests, due to weekends). Again on a note of practicality, given the number of students isolating as close contacts towards the end of term, this will need between 2.5 million and 3.5 million tests per week, almost certainly significantly higher given the new variant.
On a much more important point, this is MUCH more dangerous in terms of spread of the virus in and via schools, given the high false negative rate found for LFTs. In effect, someone who has sat for an hour, maskless, sharing a desk with a positive case will continue to circulate freely in the school context (despite the fact that contact of a quarter this length, even with a mask, would lead to isolation for 10 days if it had happened outside school).
Even if they have been infected and would test positive using a PCR test, there is only a 50% likelihood (at a conservative estimate) that their first LFT will pick up their infection. There is only a 25% change that they will be picked up on the second day. Even after 5 tests, there is a 3% possibility that a positive case will have tested negative every single time.
But this infected student - who under current protocols would not have been in school for 10 days after contact with a confirmed positive, thus breaking the in-school chain of transmission - instead remains in school, creating their own chain of close contacts and potential infections, for days.
So be careful when you say 'oh, secondary schools will have mass testing, so they will be safer'. No, they will not. Initial mass testing will make them (very briefly) safer. Replacing isolation with repeated lateral flow tests will make them MUCH more dangerous in terms of viral spread.