Primary schools and nurseries will reopen to more pupils on June 1, the Transport Secretary has insisted amid fears it would be unsafe.
Grant Shapps said the Government intends to stick with a plan to begin reopening schools a week from Monday as part of measures to ease the coronavirus lockdown.
Teachers and labour unions have argued Downing Street's plan will put pupils and staff at risk, and a number of councils have rebelled and said they will keep schools closed or leave the decision to head teachers.
A group of scientists has said it would be unsafe to send pupils back on June 1 and has urged the Government to delay the move for two weeks.
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In a car crash TV interview, Mr Shapps said the Government has no intention of delaying the reopening of schools in England to children in Reception, Year 1 and Year 6 on June 1.
Regarding the June 1 target date, he told Sky News' Sophy Ridge On Sunday programme: "That's certainly the intention."
Downing Street's Covid-19 "roadmap" said the reopening could be pushed back if the outbreak was not sufficiently under control.
A final decision will come on or before May 28.
On Friday, the Government published documents from the Scientific Advisory Group for Emergencies (Sage), which looked at the scientific modelling for seven different scenarios for school closures.
None of the published scenarios looked at the plan to reopen schools in England to children in Reception, Year 1 and Year 6 from June 1.
One document said the evidence on how likely children are to transmit Covid-19 remains "inconclusive", but the balance of evidence suggests that it may be lower than in adults.
Teachers do not appear to be at above average risk compared with other occupations, Downing Street's scientific advisers have suggested, although there is still a chance they can transmit the virus.
Following the publication of the papers, teachers' unions called on the Government to explain how it is safe for children and staff to return to schools in England next month.
One union leader accused Boris Johnson of taking a "cavalier attitude" towards children, while another union called evidence from the Government's scientific advisers "inconclusive".
Last week, a group called Independent Sage, led by Sir David King, who was the chief scientific adviser under former prime ministers Tony Blair and Gordon Brown, said June 1 would be too soon
It claims the risk to children would be halved if ministers delayed the planned reopening by two weeks.
It is hoped by then an effective coronavirus test, trace and isolate programme will be in place, said the independent group of scientists.
Meanwhile, former Ofsted chief inspector Sir Michael Wilshaw said it is time to reopen schools, but warned it is "critical" that parents are confident it is safe to do so.
He also admitted that trying to enforce social distancing among young children - a concern voiced by many teachers and critics of the Government's plan - would be "like herding cats".
He said it might be necessary to consider cancelling summer holidays and for some pupils to resit the year.
Sir Michael told Sky News: "It is all right opening up schools but if parents lack that confidence they are not going to send (children) in.
"It seems to me that the Government have got a real part to play here making sure that parents have the evidence."
He said he understood why some teachers are reluctant to reopen schools, adding: "Social distancing with five-year-olds is a bit like herding cats.
"It is really important that the Government get the confidence of parents and teachers and they should lay down very clear guidance and rules under which schools should operate."
Sir Michael said local authorities should be given the responsibility of policing safety standards once schools reopen.
Research showed that disadvantaged students had suffered the most from the shutdown, he added.
He claimed the UK could see a "lost generation" of young people as a result of the shutdown, and criticised Ofsted for failing to monitor schools' remote teaching practices during the lockdown.
Shadow policing minister Sarah Jones said the Government needed to say whether it had rowed back on its promises of having a track and trace system in place by this week.
Ministers have outlined plans for a 25,000-strong team of manual tracers to start work by June 1, but they will not be aided by an NHS Covid-19 symptoms app which had been promised by "mid-May" by Health Secretary Matt Hancock.
Labour has said schools should go back but only when an effective track and trace system is in place.
Devi Sridhar, professor of global public health at Edinburgh University, said it is not a question of whether it is safe to open schools but "is it safe enough?".
She told Sky News: "What is the threshold of risk that is acceptable?
"I think the three principles to follow with schools is the first is to be completely honest with teachers and parents about the scientific uncertainty.
"We know children carry the virus, we don't know the degree they transmit it to adults, we also don't yet know how rare it is for children to have this delayed, inflammatory, multi-syndrome condition which means that some weeks after exposure to the virus they have this severe inflammatory reaction."
Professor Sridhar said a proper testing and tracing system is needed to halt the transmission of the virus and quickly identify any clusters in schools.
Germany is testing children as they arrive at school to make sure cases are caught as they emerge, she added.
Decisions should be made at a local level given that the UK's outbreak is worse in some areas such as the North East of England.
Schools, colleges and nurseries across the UK closed more than eight weeks ago due to the coronavirus outbreak, remaining open only for vulnerable pupils and the children of key workers.
Mr Johnson unveiled proposals to allow more children in Reception, Year 1 and Year 6 to return to school in England from as early as June 1 as part of his strategy for easing lockdown restrictions.
It is his hope that primary schools will be open for children of all ages by the end of June, giving them a month of lessons before the summer break.
The Government has also said secondary schools and colleges should aim to offer some "face-to-face contact" with Year 10 and 12 students who have key exams next year during the summer term.
But the devolved administrations in Scotland, Northern Ireland and Wales have adopted different approaches to sending children back to the classroom.
In Scotland, schools will reopen towards the end of the summer holidays, but children will return to a "blended model of part-time in-school and part-time at-home learning" to allow for social distancing.
The Welsh Government has not given any dates for when the country can expect schools to reopen.
In Northern Ireland, all children are intended to restart classes on a phased basis, involving a mixture of physical attendance and remote learning, in September if enough progress is made in curbing coronavirus.
But the education minister has said schools in Northern Ireland could reopen to pupils preparing for exams in the third week of August.
