Millions of children and their families are being asked to take Covid tests as schools reopen this morning, even if they show no symptoms.

Primary school pupils are exempt from the tests, which are being extended to secondary students and anyone in their household – including relatives and childminders.

The Government hopes that mass testing and isolation will help identify asymptomatic Covid cases, which are thought to make up a third of all infections.

High schoolers and college students will receive their first three tests under supervision at their learning institution.

Thereafter, they and their households will be provided with home tests to take twice weekly, reporting their results online or via 119 to NHS Test and Trace.

Those reporting positive test results will be asked to self-isolate, inform their school or college and book a laboratory-based PCR (polymerase chain reaction) test at a Covid testing centre.

'Most of us ... would expect a positive to mean ‘yes’ and a negative to mean ‘no’.'

The home-based lateral flow tests involve swabbing the throat and nose, dipping this swab in a solution and placing two drops on a device somewhat similar to a home pregnancy test.

Results appear within half an hour, but the accuracy of these results have been criticised by some experts – cases of negative self-testers becoming unwell with Covid the next day have been reported.

Jon Deeks, professor of biostatistics at the University of Birmingham, said in January: “Most of us have never done a diagnostic test in our lives ourselves, and we would expect a positive to mean ‘yes’ and a negative to mean ‘no’.

“But here a positive means ‘probably’ and a negative means ‘we really can’t tell’.”

The families and support bubbles of primary school pupils are being asked to get their tests through a number of other routes.

These include through their employer if offered, at a local test site, collecting a home test kit from a test site or ordering kits online.