The majority of schools using rapid lateral-flow Covid tests did not detect a single case of the virus, early findings seen by Tes suggest.
Headteachers say the findings add to the concern that the Department for Education is relying on a test that will miss positive Covid cases, as part of its plan to manage the virus in schools.
Figures from 24 schools where around 2,000 students have been tested show that just five cases of the coronavirus were found in pupils across five different schools.
Some 19 schools – almost 80 per cent of those that provided figures – did not find a single case using the tests that the Department for Education has sent to schools.
Data from the WorthLess? campaign group of headteachers also shows that tests on around 2,500 staff across 23 schools identified just three positive cases of the virus.
One school has also reported that four members of staff who tested negative using the rapid test have since tested positive for Covid-19 after having a PCR test.
Taken together, the figures from the WorthLess group show that 0.18 per cent of the tests taken resulted in positive results.
Clive Sentance, a member of the WorthLess group, said: "Our figures support the concerns that lateral-flow tests miss some positive cases, because they were never designed for infection control.
Coronavirus: Fears over the reliability of Covid tests in schools
"On the testing of close contacts, there is a concern about no longer asking pupils to self-isolate."
Mr Sentance, who is the principal of Alcester Grammar School in Warwickshire. added: “In our setting, we know when we asked people to self-isolate that, by and large, they did as asked. This was successful in nipping things in the bud so we are very concerned about stopping this when it worked."
The new figures come amid controversy about the Department for Education's plan to use the lateral-flow Covid tests to keep close contacts of Covid cases in schools.
The government has sent testing kits to secondary schools and colleges and is set to roll-out the programme to primary schools.
Secondary schools and colleges have been told to use the tests for:
- Initial testing of vulnerable pupils and children of critical workers who are on school and college sites (two tests, three to five days apart).
- Weekly testing of staff who are on school and college sites.
- Daily testing of close contacts of positive cases in school and college as an alternative to self-isolation.
However, there are growing concerns about the use of the tests to keep close contacts of confirmed cases of the virus in school rather than asking them to self-isolate.
Tes revealed on Friday that public health directors were advising schools not to use the tests in this way, as the DfE has instructed, but to continue sending pupils or staff home to self-isolate if they come into contact with the virus.
There is also concern among scientists that the lateral-flow tests will give false negatives, meaning people with Covid remain in schools.