The planned reopening of schools in England has descended into disarray, as unions advised teachers not to return to the classroom, heads took legal action over the government’s plans and senior Tories warned that school gates may have to remain shut for weeks to come. With warnings that some primary heads would arrive at work on Monday morning unsure about whether they would be able to reopen to pupils, teachers accused the government of making an “utter shambles” of school reopening and demanded a last-minute delay. Gavin Williamson, the education secretary, was also facing renewed calls to resign over the chaos. There are growing demands this weekend for teachers to be given swifter access to the Covid vaccine and for schools to gain greater military help in testing pupils safely and reliably. Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), told the Observer: “The people I represent will be going into their schools and colleges on Monday not knowing precisely which staff they may or may not have. There is significant uncertainty. It may well be that there are lots of school leaders who will be writing to parents saying, ‘We don’t know what we can do on Monday, your children shouldn’t be coming in’. “It is obvious to everybody that the government has made an utter shambles of the arrangements for the start of the spring term with late and confused communications, and the lack of a clear scientific rationale.” Some Conservatives believe that a delay until the February half-term may be needed. Jeremy Hunt, the former health secretary, said: “It is massively risky to open schools when so many parts of the NHS are teetering on the brink. The economic and human impact of keeping them closed is severe – but so too is the impact of thousands of wholly avoidable extra deaths. So I wouldn’t be surprised if we end up effectively keeping the majority of schools closed until the February half-term.” The fallout from teachers was fuelled by the revelation last week that the government’s Scientific Advisory Group for Emergencies had warned ministers that it was “highly unlikely” that the pandemic could be brought under control if schools opened this week. The National Education Union (NEU) is advising primary school staff it is unsafe to head to classrooms on Monday, when most are scheduled to return. The move will force some schools to switch to online learning for the majority of their pupils. The union said on Saturday that all primary and secondary schools should remain closed for two weeks after the Christmas break. The NASUWT teachers’ union and the ASCL have also called for a temporary nationwide move to remote education for the vast majority of pupils. Meanwhile, the National Association of Headteachers (NAHT) and the ASCL have begun legal action against the government, demanding it reveal the safety evidence for its reopening schedule, given the higher transmissibility of the new Covid variant. Paul Whiteman, general secretary of the NAHT, said: “Headteachers are in an impossible situation. The government’s simplistic approach of ‘schools gates open’ or ‘school gates closed’ means they’re hamstrung. It’s going to be a difficult couple of days. We hope the government brings clarity as soon as possible this weekend, or early next week.” The crisis heaps further pressure on Williamson, who faced calls to quit over his handling of last summer’s exams. He has already reversed his decision that primary schools in some parts of London should open on Monday. Ed Davey, the Lib Dem leader, said: “It is now beyond doubt that Williamson is the worst education secretary for a generation. From March this government has continually failed our children and young people, at a huge cost to their futures. He must go.” Barton said: “Lots of people in school and college leadership know that they are held accountable for what they do – and that if they were to lose the trust of their staff to the degree that I think the secretary of state has lost the trust of the profession, they would definitely be considering their own positions. There is an alternative. Get a grip on this, work with the profession and do it quickly.” The government now expects schools and colleges to have fully reopened from 18 January. Most primaries in England are due to reopen from Monday, except those in local authorities termed “contingency frame areas” with high rates of Covid transmission. English secondary pupils in exam years are scheduled to return to schools from 11 January, with other year-groups taught remotely. Bernard Jenkin, a Tory MP who has been pushing for greater military help for testing in schools, said: “I’m afraid Gavin Williamson has not handled this well. Schools need a breathing space. They should never have been asked to take charge of testing in schools. Keeping universities and schools closed for a few more weeks may turn out to be a price well worth paying in order that we can concentrate on getting the vaccine out, rather than having a crisis in the health service. We might be looking at mid-February for the schools going back now.” Robert Halfon, the Tory chair of the education select committee, called for greater military involvement to improve school testing and teacher vaccination. “We have to decide as a nation, are children our number one priority, or not?” David Davis, the former Tory cabinet minister, said special educational needs teachers should be given “special dispensation” for an early vaccine. A Department for Education spokesperson said: “We want classrooms to reopen wherever possible in the new term. “We will move to remote education as a last resort, with involvement of public health officials, in areas where infection and pressures on the NHS are highest.”