England’s biggest teaching union has described the prime minister’s announcement tonight that primary schools could reopen to more pupils after half term as “nothing short of reckless”.

In an address to the nation, Boris Johnson has said that primary schools could open after half term for pupils in three year groups.

But the leaders of teacher and school leader unions have expressed serious concerns over the plans.

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Mary Bousted, NEU teaching union joint general secretary, said: “We think that the announcement by the government that schools may reopen from June 1 with Reception and Years 1 and 6 is nothing short of reckless.”

“Coronavirus continues to ravage communities in the UK and the rate of Covid-19 infection is still far too great for the wider opening of our schools.

“A study published last week by the University of East Anglia suggested that school closures are the single most effective way of suppressing the spread of the virus.

“If schools are to reopen, we need the government to meet the five tests we have set to keep children, their families and our staff safe.

“There must be much lower numbers of Covid-19 cases, with extensive arrangements for testing and contact tracing to keep it that way. This test has manifestly not been met.

“We must have a national plan for social distancing, hygiene, appropriate PPE [personal protective equipment] and regular testing to ensure our schools and colleges don’t become hotspots for Covid-19. This test has manifestly not been met.

“And there must be plans drawn up to protect vulnerable staff, or those who live with vulnerable people, to stop more educators or members of their families dying of this dreadful disease.”

Dr Patrick Roach, general secretary of the NASUWT teaching union, said that leaving choices about how to reopen safely up to individual schools would be “baffling” given that the government had previously closed all schools on public health grounds.

He said tonight’s announcement was likely to “provoke confusion” and lacked the clarity of ministerial statements in Scotland and Wales.

It could result in “thousands of schools rushing to make decisions about how best to safeguard the health and safety of children and staff in the absence of any clear national guidance”, he said.

He added: “Unless and until the government can demonstrate that schools will be safe for staff and children, all schools should continue to limit their opening only to vulnerable children and to children of key workers.”

Heads have also raised concerns over the proposals, saying that the idea of personal protective equipment has been “dismissed” and that they are not “persuaded” that now is the right time to reopen schools more broadly.

Geoff Barton, general secretary of the Association of School and College Leaders, said: “We are concerned about the idea of reopening primary schools to significantly more children after half term.

“It is not clear to us how the reintroduction of such significant numbers of pupils in primary schools can be safely managed, particularly considering that Reception and Year 1 comprise very young children with whom social distancing is extremely difficult.

“And we are worried that personal protective equipment in schools has so far been dismissed, leaving an over-reliance on social distancing in environments where this is inherently problematic.

“We are not trying to impede the reopening of schools. Throughout the crisis, we have highlighted the importance of bringing in more pupils when the time is right to do so and there is a clear plan in place to manage it safely.

“Unfortunately, we are not persuaded that either of these two simple tests has yet been met.

“We welcome the prime minister’s assurance that this timescale is not set in stone and will be postponed if necessary, and we will continue to work constructively with ministers and officials, as we have done throughout this crisis.”

The difficulties of implementing social distancing measures with younger pupils have been highlighted extensively in recent weeks.

Paul Whiteman, general secretary of the NAHT school leaders’ union, said in response to tonight’s announcement: “School leaders do not want to see classrooms empty for a day longer than they need to be. But there is not a school leader in the land who wants to risk admitting more pupils unless it is perfectly clear that it is safe.

“The government must not lose sight of the fact that in many cases it may be physically impossible to bring back the number of pupils being suggested and maintain any sense of social distancing, especially in infant schools and small schools.

Mr Whiteman said schools would be “inundated” by questions from anxious parents about what the announcement meant. He said there had been no explanation of why reopening schools would be considered safe, but that, with 1 June considered the earliest possible opening date, the government had a “small window” of time to explain the basis behind the proposals.