NHS and social care staff, food producers and delivery drivers, along with utility workers are among a list of workers deemed "essential" to the coronavirus response.
Also included in the key workers list include police, supermarket staff, teachers and public transport workers.
The Department for Education said: “If your work is critical to the COVID-19 response, or you work in one of the critical sectors listed below, and you cannot keep your child safe at home, then your children will be prioritised for education provision.”
It added that children with at least one parent or carer identified as critical workers by the government could send their children to school if required.
The Department for Education said they expected the majority of educational establishments to stay open where required – but recognised it may be “impossible” for small rural schools.
It said when a school is unable to stay open, it would work with local officials to find an alternative setting for pupils, as well as providing transport arrangements.
On Friday, Health Secretary Matt Hancock warned that coronavirus will continue to spread if people continue to socialise.
He said: "If you stay at home you are saving lives.
"I know, of course, this is a more dangerous disease for older people but not exclusively, some young people get it too."
He added: "So, we're urging people to follow the public health advice. In the emergency Bill that's in front of Parliament right now, we are taking the powers to be able to enforce these measures, so we can make it happen by law if we need to.
"I'd rather not do that and the evidence so far is that the vast majority of people are following the advice, are doing what is sensible and right."
The list has been separated into eight categories, including health and social care, key public services – such as those essential to the running of the justice system, religious staff, charities and journalists – and transport.
Those involved in food production, processing, distribution, sale and delivery are also included, along with “administrative occupations essential to the effective delivery of the Covid-19 response” in local and national government.
Staff needed for “essential financial services provision”, such as bank workers, key telecommunications staff and postal services and delivery workers are also on the list.
Many English schools will close on Friday afternoon until further notice, along with nureries, colleges and childminders.
Special schools will remain open, while educational settings will continue to cater for vulnerable children and pupils whose parents are key workers.
All schools in Scotland and Wales will close on Friday, while Northern Ireland's schools will follow suit and close from Monday.
GCSEs and A-levels in England and Wales will be cancelled – although Prime Minister Boris Johnson said there were plans for students to receive qualifications.
The Education Secretary has indicated guidance about exam cancellations will be issued on Friday, including how pupils unable to sit their exams will get their grades.
Gavin Williamson said the Government would work with schools, colleges and England’s exams regulator, Ofqual, “to ensure children get the qualifications they need”.
School leaders have said they expect that grades will be based on teacher assessment and evidence of internal assessment – such as mock exams – which could then be submitted to the exam boards to check.
Paul Whiteman, general secretary of NAHT which represents leaders in the majority of schools, said: “The government has made clear that every child who can be safely cared for at home should be. And their advice makes clear too that this applies to children of key workers.
“For the vast majority of children and young people, school buildings will close tonight and not reopen for the foreseeable future.
“Taking up a place at school during this time of wider closure is the offer of last resort, for the minority of key workers, who have no alternative.
“School leaders have many questions that remain unanswered about how this will work in practice. We will continue to work with the government throughout the day to provide greater clarity to schools to enable this reduced offer to be up and running as soon as possible.”
Coronavirus: Everything you need to know: