Britain could be hit with coronavirus for "a year or more" meaning pupils could be home for "months and months" if they do not return to school next week, the Education Secretary has said.
Gavin Williamson doubled down on ministers' plans for a June 1 start for primary pupils in Reception, Year 1 and Year 6.
It comes as the Prime Minister insisted schools will reopen in six days time despite teaching unions and a string of councils opposing the move on safety grounds.
Boris Johnson also said on Sunday that up to a quarter of Year 10 and Year 12, who face GCSE and A-level exams next year, can expect to have "some contact" from June 15.
Addressing the ongoing row over the plans, Mr Williamson told BBC Breakfast: "We cannot be in a situation where we go for months and months where children are missing out on education."
He added that the Government "realises there will be an initial nervousness about the return of schools" but said he was "very confident a large number of schools will be reopening all the way through next week".
He insisted official guidance, which urges teaching pupils in small "bubbles" of no more than 15, ensures a "maximum amount of safety".
It comes after the PM acknowledged in Sunday's Downing Street briefing that it may "not be possible" for all schools to restart from the start of June.
But some 50 councils in England are reportedly ready to defy the reopening date, the Sunday Telegraph reported.
Teaching unions, which have been at loggerheads with ministers, also refused to back down after the announcement, placing the plans in further doubt.
Teachers’ union NASUWT said the decision to push ahead with the June 1 opening was “at odds” with scientific evidence on transmission.
NASUWT general secretary Dr Patrick Roach said: “The Government has to recognise that it has not won the trust and confidence of the teaching profession.
“Notwithstanding the Government’s assertions, the bottom line is that no teacher or child should be expected to go into schools until it can be demonstrated that it is safe for them to do so.
Kevin Courtney, joint general secretary of the National Education Union, which has over 45,000 members, said it remained opposed to the June 1 date.
Geoff Barton, general secretary of the Association of School and College Leaders, said it was "worrying" that the test, track and trace strategy is not yet ready.
The PM said the Government "will engage" with authorities and unions and said a "final decision" for schools would be announced during the three-weekly lockdown review on Thursday.