(Bloomberg) -- Boris Johnson’s chief adviser has spent a decade waging war on Britain’s teaching unions. Now he needs their help.

The prime minister wants England’s schools to partially reopen from June 1 as he eases the coronavirus lockdown, but teachers say their concerns over safety and practicalities should be addressed first.

While other parts of the government’s virus response have seen close engagement with labor unions, the tone has been more confrontational on schools as ministers and their supporters in the media attack teachers for their stance.

Dominic Cummings, Johnson’s most senior adviser, is now most famous as the man who ran the campaign for Brexit, but before that he was one of Michael Gove’s chief aides at the Department for Education.

There, the two men made it their mission to break up what they said was a cosy relationship between teachers and officials that made it difficult to reform schools. Teachers were attacked as “militant” and accused of being part of a “blob.” Critics of education policy were harangued on social media by an official Conservative account.

Whether the pair were successful in reforming education is hotly contested. That they upset people isn’t. Gove was moved from the department ahead of the 2015 election as then-prime minister David Cameron tried to mollify angry teachers and parents.

Under Johnson’s plan for lifting the lockdown, primary schools, which take children up to the age of 11, would partially reopen, with just the oldest and youngest children. To enable some level of social distancing, classes would also be cut to half the usual size. Secondary schools have been asked to provide face-to-face contact for children who have major exams scheduled next year.

Schools are wrestling with how to meet the requirements. Splitting classes across different rooms will need more teachers, while children who aren’t allowed back will still need to be taught remotely. And there are questions over protecting staff who are vulnerable to coronavirus, and what to do about outbreaks.

With just over a week to go, it was still unclear Friday how many schools would reopen. They haven’t yet formally been asked to -- only to prepare for the possibility -- and the Department for Education said it has no estimate of how many would open. The Guardian newspaper named eight local authorities whose schools aren’t immediately planning to.

Lawrence Waterman, chief executive of the British Safety Council, which campaigns for safer workplaces, said the government was wrong to choose an “arbitrary” target.

“The idea that you do it across the whole country like a steamroller is denying the professionalism and the engagement of the individual groups of teachers that need to confirm that their particular school is properly set up for it safely to reopen,” Waterman said in an interview. Johnson’s government is “broadcasting to the unions but not inviting them in for meetings. If you really want to take teachers with you, you need to show respect for them.”

Teaching unions have a long history of disagreements with Conservative governments. When Margaret Thatcher was education secretary in the 1970s, she believed the National Union of Teachers to be under communist influence. When she was prime minister, there were more than two years of industrial action, culminating in a national strike in 1986.

Labour governments have generally been closer to teachers, and senior union officials were issued with security passes allowing them into the education department in the 2000s -- a policy Gove swiftly ended.

The mutual distrust hasn’t improved during the coronavirus crisis.

In March, as ministers rushed to close schools -- keeping them open only for vulnerable children and those whose parents were key workers -- head teachers had to wait until late in the evenings for guidance. Sometimes they were only told how they were expected to implement policy changes with a few hours’ notice.

One union official, speaking privately, contrasted the Department for Education’s approach with the way the Treasury invited senior union representatives to discuss its virus mitigation strategies as they were being developed.

Instead, the official said, teaching unions only learned about policies affecting their members when they were announced to the public.

The Department for Education didn’t dispute this, but said in a statement it had “engaged closely with a range of relevant organizations, including the unions, throughout the past eight weeks, including organizing for them to hear directly from the government’s scientific advisers last Friday.”

The government has pledged to publish the scientific advice supporting its view that it is safe to reopen schools this Friday.

But the discussion is being conducted in a heated atmosphere, with the Daily Mail newspaper, which supports lifting the lockdown, using its front page to launch daily attacks on teaching unions as “callous” and “cynical.”

Polls suggest the public doesn’t agree. YouGov reported May 18 that 50% of adults opposed the school reopening policy, and only 36% supported it.

©2020 Bloomberg L.P.