All English secondary schools have been asked to provide an on-site test for students returning this week.
Secondary schools pupils in England will be tested for Covid at least once before rejoining classes for the new term, the government has said.
Ministers have assured schools that testing kits will be provided as needed and urged pupils to test twice weekly.
It comes as the government stressed on Sunday that nothing in the Covid data suggests new restrictions are needed.
Meanwhile, Education Secretary Nadhim Zahawi has said face coverings will be required in schools until 26 January.
The new on-site testing rules will be limited to England, where pupils will begin returning to schools for the new term later this week.
In Scotland and Northern Ireland, students are already being asked to test twice every week.
The Welsh government has urged staff and students to test three times per week before the start of the new term.
In a statement announcing the measures, Health Secretary Sajid Javid said “regular testing is a key way to support schools and protect face-to-face teaching”.
Fears have been raised in recent that a wave of illness and isolation among staff caused by the new Omicron coronavirus variant could make it “impossible” for schools to deliver face-to-face teaching to all pupils.
In a bid to combat a potential surge of illness, ministers have urged pupils to come forward for a Covid vaccine.
Mr Zahawi outlined his plan to keep schools open despite the surging number of cases in a Twitter thread.
He said education is the “number one priority” for the government and he wanted to “offer some reassurance”.
As well as testing, Mr Zahawi promised “a further 7,000 air-cleaning units will be provided, building on the 1,000 already announced and the 350,000 CO2 monitors distributed to classrooms across the country”.
The education secretary said he had also asked teachers who had left the profession or retired to come back as temporary support and urged all 12-15 year olds to get both doses of the Covid vaccine and for older children to get their booster jabs.
But Labour’s shadow education secretary, Bridget Phillipson, criticised ministers for the slow rollout of jabs to schoolchildren.
She said almost two million students aged 12-17 remain completely unvaccinated and the government had missed “the chance to get ahead of the virus, and is letting down our children”.
Meanwhile, government ministers pushed back over the weekend against suggestions that fresh coronavirus restrictions will be necessary in the coming weeks amid a surge of new infections caused by the Omicron variant.
Cabinet Office minister Steve Barclay said the government believes that significant behaviour changes among members of the public mean further restrictions are not necessary.
“The widespread use of testing is an illustration that the British public are taking sensible steps to keep themselves safe to keep their friends and family safe,” Mr Barclay said.
England’s current restrictions are due to expire on 26 January, although a review is expected in the next few days.
On Sunday, England and Wales recorded 137,583 daily cases and 73 deaths within 28 days of a positive Covid test. Data for Scotland and Northern Ireland is due to be updated after the bank holiday weekend.
The latest figures for England are down on the 162,572 new cases reported on Saturday, which had been a record number for the fifth day in a row.
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