Primary schools in England could reopen from 1 June - and the safety approach closely follows Denmark's example, where schools opened last month. This assumes that social distancing will be unreliable with young children, so instead children stay in small groups all day, in "protective bubbles".
Re-opening schools is going to be one of the biggest symbolic steps towards loosening the lockdown.
It has divided opinion about whether it can be safe - and who should go back first.
But there are places, such as Denmark and Germany, where it's already happened.
"There was anxiety in the community," says Dom Maher, head of the international section of St Josef's school in Roskilde, on the Danish island of Zealand.
"A large percentage of parents were in two minds," he says. "And there were some who decided to wait a few days to see."
But several three weeks after re-opening, he thinks it has worked better than might have been expected.
Children were relieved to be back and parents have become more confident about safety - and numbers attending schools have steadily risen.
Primary school children have returned first in Denmark, and a system is in place to keep children in small groups and with as little contact with others as possible. They spend their school day in a kind of virtual cocoon, with no cross-over with others.
These micro-groups of pupils arrive at a separate time, eat their lunch separately, stay in their own zones in the playground and are taught by one teacher.
There are about a dozen pupils in these groups. Social distancing means that's about the maximum number who can go into one room, which requires dividing classes and teaching staff.
"Most schools in Denmark are structured where you have primary and lower secondary in the same school," says Mr Maher. That means there is space to spread out, with only about half of the usual thousand pupils on site.
"We've had enough classrooms to do that - if school opening went ahead where all students were back, it would be a real struggle," says the head.
"We wouldn't have enough classrooms and would have to start doing morning and afternoon shifts."
The other lynchpin of the Danish approach is a huge amount of hand washing and sterilising.
"There is pretty much hourly washing going on," says, Mr Maher, so much so that the new problem is skin irritation and eczema.
But he says the idea of perfect social distancing with small children is not realistic.
"Most of them are pretty good with it and mindful of space. But they do forget," he says.
There are no face masks - either for pupils or teachers.
Dorte Lange, vice president of the Danish Union of Teachers, says this lack of personal protection hasn't been an issue, because the medical advice has focused on the strategy of keeping pupils distanced, in isolated groups, and a strong emphasis on hygiene.
"We are glad to say the re-opening up to now has been quite successful," the union leader told the BBC.
Teachers who have health issues, or who have family members who might be at risk, can teach online from home, she says.
Some of the Danish and German ideas:
- Younger children back first in Denmark - older students in Germany
- Smaller groups of students so social distancing can be maximised
- Groups maintained for duration of the day
- Regular breaks for hand-washing
- In Germany, face masks in communal areas in line with the national plan
But she suggests the mood has shifted towards wanting to get children into school again.
"We can see many of the older students are not thriving at home. They really need to be back in the community of the school," she says.
There has been a collective approach to re-opening between teachers' unions, local authorities and government, says Ms Lange.
If a further opening of schools were to increase the rate of infection, she says there would have to be a change of plan.
"But if they say it's safe to open for older kids, we'll make it possible."
There are still worries among parents, including a Facebook page with worries about not treating children as "guinea pigs".
Sirin posted to say she has kept her four-year-old at home despite the re-opening, but her daughter "asks me every day when she's going to kindergarten again and that she misses her friends so much".
"So I thought about sending them off in about two weeks - since I don't think this virus will be gone for a long time and I have to start working at some point."
Another mother says she feels pressured into sending her child into school. "I'm not comfortable with it. And I have my grandma who's on vacation with us."
On Copenhagen's waterfront there is a one-way sign into a school, indicating the highly-structured nature of the Covid-19-shaped school day.
Ida Storm Jansen, an administrator in Copenhagen International School, says about 10 students are allowed per classroom. It's an international school but all such schools have to follow their countries' health advice.
"I had a great conversation with a four year old. He said we used to sit on the carpet and now we sit on the tape marks," she says.
The system of isolating these small groups of children is more practical than only relying on social distancing, she suggests.
"Frankly it's impossible. When they play, of course they forget," she says.
But with constant hand washing and minimal contact with any other group, she says there is an effective system - and children have adapted to it very quickly.
Ms Jansen says fears of a "big backlash from parents" over re-opening didn't materialise - and children were relieved to be back with their friends.
No 'business as usual'
When some schools opened in Germany last month, the detail of planning went down to individual seating plans.
Shaun Roberts, principal of the Cologne International School, says there is a fixed place for each student - so that if someone is found with the virus, the contact tracers will know exactly who was sitting nearest.
In Germany, it's the oldest year groups which have gone back first. The top class is revising for the Abitur, the German equivalent of A-levels, which have not been cancelled.
Exam halls are one of the few locations which lend themselves to social distancing.
There is a one-way system in the corridors to minimise contact, break times are staggered, there is a strict cleaning regime - and face masks are worn in common areas.
"People do what they have to do without making a fuss," says Mr Roberts. But it isn't "business as usual".
The school days are shorter and mixed with online lessons, so different year groups can share classrooms which might now only hold 10 pupils.
And there are staff and pupils who are staying at home because of their health issues or because of concerns about someone in their family.
"The great unspoken", he says is that schools might have re-opened, but there are limits to what can be provided.
France and The Netherlands will be the next to open schools next week - with strong opinions for and against returning. And plans for schools in the UK will become clearer in the next few days.
Mr Roberts in Cologne describes it as a "journey back to normality", which will continue long beyond the summer break and into the autumn.
It might only be beginning - but he says, it has to start somewhere.