The government has published its safety plans for the return to school in September - built on the principle of keeping classes or whole year groups apart in separate "bubbles".
But it means if there are two confirmed coronavirus cases in 14 days, all the pupils in that group, or even the whole school, may have to be sent home.
Schools will have testing kits to give to parents if children show symptoms.
Mobile testing units will be sent to schools which have an outbreak.
The safety plans issued by the Department for Education say that "given the improved position, the balance of risk is now overwhelmingly in favour of children returning to school".
The guidance sets out how schools will operate with all pupils back full time. This will be with an expansion of the "protective bubble" system already used in schools and minimal contact between groups.
The new rules for autumn will mean:
grouping children together in groups or "bubbles" in primary this will be a class, in secondary a year group avoiding contact between these groups during the school day separate starting, finishing, lunch and break times attendance compulsory with the threat of penalty fines regular cleaning of hands those with symptoms told to stay out of school no big group events like school assemblies arranging classrooms with forward facing desks separate groups on school buses discouraging the use of public transport masks not expected for pupils or staff.Notably, all schools will have to draw up plans for the possibility of local lockdowns.
Education Secretary Gavin Williamson said this week: "It's "not about one metre, it's not about two metres."
Earlier this week, Mr Williamson told the BBC that parents in England who do not send their children back to school in September will face fines "unless there's a good reason for absence".
What happens if there is an infection or pupils with symptoms?
If a child in school has Covid symptoms they will have to be taken home straight away, and staff waiting with them will have to wear protective equipment.
All schools are being promised testing kits to give to parents - and if there are two confirmed cases within 14 days, or a rise in absences because of Covid-like symptoms, this could be counted as an outbreak.
This could mean other pupils in the class or the year group being sent home. It could escalate to the whole school site being shut down - but the guidance says such whole-school closures "will not generally be necessary".
A mobile testing unit could be sent to a school with an outbreak, which could carry out tests to see whether an infection had spread, which could check a class, a year group or the whole school.
In the event of a local outbreak, health protection teams or local authorities may advise schools to close.
What are schools saying about the plans?
"The logistics of keeping apart many different "bubbles" of children in a full school is mind-boggling," said Geoff Barton, leader of the ASCL head teachers' union.
"There just needs to be a sense of reality about what is possible," he said - and called on the government to have a "Plan B" if the return proved unworkable.
Head teachers have also voiced concerns about penalty fines being issued to parents if they do not send their children back to school.
Michael Ferry from St Wilfrid's Secondary School in Crawley, West Sussex, called the threat of fines "ludicrous" and said that he will not issue them "in any shape or form".
"A significant amount of our community has been affected by the closure of Gatwick airport and if I fine parents £120, I'm effectively saying I'm taking away eight school meals vouchers - because that's what it amounts to," he told BBC Breakfast.
He also warned that the school "cannot be full" on any given day, if pupils and teachers face any level of social distancing.
However, Ashley Harrold, head of secondary school Blatchington Mill School in Brighton, said schools could "overcome" challenges around capacity - although there were still "legitimate questions around safety".
His school had drafted four plans designed to bring all pupils back without shrinking the curriculum.
How have parents reacted?
"I am a parent, and will not be sending my child back to school, if it is not safe to do so," Anthony told the BBC, when draft plans were revealed this week.
But Kirsty said: "Everything has got to start to go back to some sort of normal sooner or later. It's worrying but I think children need the stability of school and the social aspect of seeing their friends."
Image copyright Getty Images Image caption Parents have raised questions about how pupils will stay apart on transportThe issue of transport to school was raised by a number of families - with questions about how that would work with "bubbles".
"Living in a rural area, my sons get a three-carriage train to school with 70 other boys and girls across all secondary year groups (and Joe Public)," wrote Iain.
"Moving start times by 15 minutes here and there will make no difference to the train they catch in the morning - so how do you 'bubble' that?"
"Transport to and from school a real concern too, packed like sardines on school buses, with no additional funds for more buses. Where will the funds for cleaning come from?" said Geraldine.
Another highlighted that families could have worries about relatives. "Some grandparents live with their children and grandchildren. Some of us parents are at higher risk than others," said Ade.
There are also questions about how the bubble system will operate when families might have children in different year groups.
"The government have made everything blurred and while there is no vaccine the risks are still huge. I'll keep mine off until I'm sure of safety. Fine me or whatever - I'm looking after my family," said Eddie.
But Ian said: "Just send them back as normal and let them get on with it for goodness sake."
Sticking with all GCSEs and A-levels
The plans for returning also recognise that pupils need to catch up after many months out of school.
This means a "modified" timetable for the first term, with an emphasis on the core subjects of maths and English. A regular curriculum will not return until the summer term in 2021.
Image copyright Getty Images Image caption Most pupils will be expected to carry on with a full range of GCSE and A-level subjectsBut for pupils taking A-levels and GCSEs, the expectation is that the full range of subjects will continue to be taken.
England's exams regulator, Ofqual, has drawn up plans to try to make the exams system fairer for those due to sit GCSEs and A-levels next year.
While there will not be a reduction in subject content, there may be more choice of questions on exams paper allowing for the fact that some pupils will not have covered all elements of their course because of school closures.
However, there will be no reduction in content of exams, as some have asked for, and maths, English and the sciences will see no changes to the exams.
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