Boris Johnson was careful to lavish praise on teachers as he visited two schools in east London on Monday before he heads off to Scotland for a holiday. The prime minister professed himself “very impressed by the work that the teachers have done, working with the unions, to make sure that all schools are safe to go back to in September”. Yet the teaching unions – and Labour’s leadership – can expect to find themselves in the prime minister’s sights once again if next month’s reopening of schools in England doesn’t go to plan. Johnson wrote in the Mail on Sunday that “keeping our schools closed a moment longer than absolutely necessary is socially intolerable, economically unsustainable and morally indefensible”. He might have added that it would be politically disastrous. In recent days, the prime minister has repeatedly insisted it is a “national priority” to get children back into the classroom. The fact he feels the need to say it suggests his polling-obsessed advisers have noticed some voters believe this hasn’t been the case up to now. The juxtaposition of reopened pubs and restaurants with thousands of primary school pupils receiving no face-to-face teaching since mid-March has irked many parents. Their irritation could turn to fury if increased transmission after the “save our summer” business reopenings stymies plans to get all kids in England back in the classroom by September. The government was understandably anxious to protect hundreds of thousands of jobs in the hospitality and tourism sectors by allowing these sectors to reopen. But ministers knew – as the government’s scientific advisers warned publicly at the time – that the plans were risky. Since then, local lockdowns have been imposed in several areas including Greater Manchester and Leicester. It is unclear whether schools would be instructed to close in similar “whack-a-mole” lockdowns once the autumn term begins. But it is hardly surprising, against that backdrop, that education unions are calling for a plan B – and for reassurances about their members’ safety. Indeed, while publicly hailing the “moral duty” to return children to the classroom, the government has already urged schools to beef up their remote learning provision in case restrictions have to be reapplied. And the “week on, week off” plan mooted by the Association of School and College Leaders at the weekend was actually modelled by the government’s scientific advisers ahead of the phased reopening of England’s schools in June – but rejected by ministers in favour of inviting pupils from selected year groups to return. If schools are unable to open in full, recent experience suggests the government will cast around for scapegoats. Some of the testiest clashes between Johnson and Keir Starmer at prime minister’s questions in recent months came over the issue of schools reopening, with the prime minister accusing the Labour leader of being silenced by the teaching unions. “The unions won’t let him say the truth. A great ox has stood upon his tongue,” Johnson said. That approach was in evidence again on Sunday, albeit in less florid language. When the shadow education secretary, Kate Green, stressed the importance of ensuring the return to school happens safely, Conservative HQ quickly issued a press release accusing her of “refusing to say it is safe for children to go back”. Johnson insisted on Monday that “basically, the plan is there” for returning children to the classroom, in full. If it fails to come off, he knows who voters are likely to blame.