A major teaching union has warned that Boris Johnson's decision to press ahead with a partial reopening of primary schools in England on 1 June is "seriously at odds" with scientific evidence about the risk of coronavirus infection to pupils, teachers and parents sparking a second wave of Covid-19.
And a second union said it would not be right for schools - which have been open only to vulnerable pupils and the children of key workers during lockdown - to open more widely at the start of next month.
Speaking at the daily Downing Street Covid-19 briefing, the prime minister made clear it was his intention to reopen early-years settings like nurseries as well as the reception and years one and six of primaries from the first Monday in June as he moves the country into step 2 of his exit strategy from lockdown. In secondaries, years 10 and 12 will start having sessions with teachers from 15 June.
All children, staff and parents will be able to access coronavirus tests if they display symptoms, he said.
But Patrick Roach, general secretary of teaching union NASUWT, said Mr Johnson had failed to reassure parents and teachers that opening schools so early will be safe and had not won "the trust and confidence of the teaching profession" for his plans.
He said: "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."
The PM acknowledged that it would not be possible to enforce social distancing rules in primary classrooms and acknowledged that some schools would be unable to open their doors to the timetable he has set out.
The proposed reopening has faced widespread opposition from unions and some councils, including Liverpool and Hartlepool, which have said their schools will remain closed.
The announcement that the government was going ahead despite these concerns came as Mr Johnson attempted to divert attention from the controversy over his senior aide Dominic Cummings’ apparent breach of lockdown rules.
The prime minister made clear that he was not sacking Cummings, who travelled 260 miles across the country to a house near his parents home in Durham at a time when his wife was already sick with the coronavirus.
Mr Johnson said that the formal decision on moving to step two of easing the lockdown would come by the legal deadline of Thursday for a nine-week review of the lockdown, when the government will also set out its assessment of its five tests for easing restrictions and give details of possible changes in rules for non-essential shops.
However, he left no doubt that this is no more than a formality, telling the daily Downing Street coronavirus briefing: "Today I can confirm I do believe we will be in a position to move to step two of our plan. As part of step two, we set out plans for a phased reopening of schools because the education of our children is crucial for their welfare, their health and their long-term future and for social justice.
"In line with the approach being taken in many other countries, we want to start getting our children back into the classroom in a way that is as manageable and as safe as possible."
Dr Roach responded: “The Prime Minister’s display of determination to press ahead with the wider reopening of schools from 1 June is seriously at odds with the scientific evidence released to date, and the deep concerns expressed by schools, teachers and parents.
“The government has yet to reassure parents and teachers that opening schools from 1 June will be safe and now appears to accept that many schools will not be able to reopen on that date. 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.
“The prime minister has rightly stressed the importance of bringing down the R rate below 1, but the evidence published to date by Sage is inconclusive when it comes to the question of whether the wider reopening of schools could contribute to a second wave of Covid-19 infections.
“The Prime Minister has also rightly made clear that he wants all businesses to be Covid-secure. However, whilst publishing limited optional guidance for schools, the government has still not made clear the standards for ensuring that all schools will be Covid-secure when they reopen.
“Teachers and the public need to be convinced that the actions by the government will not put at risk the health and safety of teachers, children or the general public.”
Kevin Courtney, joint general secretary of the National Education Union, said: "The NEU does not agree that it would be right for primary schools to open more widely on 1 June. We once again call on the Government to engage meaningfully with the education unions on these matters. We stand ready to talk to the Government about how our five tests can be met and then how we can then proceed to a safe wider re-opening of schools.”
Meanwhile, a spokesman for the National Association of Head Teachers said Mr Johnson had shown "a hint of a more realistic tone on wider school reopening" in his comments.
"That the prime minister acknowledges that flexibility will not just be possible but will be necessary is to be welcomed," said the NAHT. "We will take the prime minister at his word that schools will be allowed to react to their own local situations and will not be forced into opening or penalised if proceeding with appropriate caution. We note that the final decision on bringing schools out of lockdown is still to be made on 28 May."
The education secretary, Gavin Williamson, will continue to consult with teaching unions, local authorities and school leaders over the next week, said Mr Johnson.
He added: "I think it is important for us to be clear about the government's intentions now, so that teachers and parents can plan in earnest for schools to open a week on Monday."
The prime minister said that a range of protective measures will be taken to minimise risks, including staggered drop-off and pick-off times, breaks and lunchtimes; reducing the size of classes and keeping children in small groups that do not mingle with one another; reducing the use of shared items; and utilising outside space.
But he admitted: "Of course we recognise that full social distancing may not be possible, especially when teaching young children."
He said that secondary school pupils in years 10 and 12, who are preparing for major exams next year, will attend school in groups of about one-quarter of a year's pupils at any time.
Children will also be encouraged not to travel on public transport where possible, in line with the advice to the wider population.
Decisions on the reopening of schools in Scotland, Wales and Northern Ireland are a matter for the devolved administrations, with none expected to order a return to classrooms as early as 1 June.
Nicola Sturgeon has said schools in Scotland will begin reopening from 11 August using a "blended model" involving part-time study in school combined with some learning at home. In Northern Ireland, children are intended to restart classes on a phased basis in September if enough progress is made in curbing coronavirus. The Welsh government is expected to set out its plans by the end of the week.