Education Secretary Gavin Williamson has said keeping schools open in England is the "best course of action", despite fears about the coronavirus.
It comes as blanket school closures are being announced in European nations such as Spain, France and Ireland.
He told a head teachers' conference in Birmingham that sending all pupils home would put a big strain on key workers who would also have to stay at home.
School leaders agreed keeping schools open was the right decision.
Geoff Barton, head of the Association of School and College Leaders (ASCL), which is meeting for its annual conference, said head teachers would authorise absence if parents took the decision to keep their children off lessons.
'Exams worry'
He anticipated absences would be small in scale and similar to "snow days".
The government has said individual schools may be advised to shut by Public Health England if necessary.
Mr Barton said there was pressure from parents for more information and guidance about what might happen to national exams.
The exam season starts in early May, when the virus outbreak is expected to reach its peak, but exam regulators are urging schools to prepare for public exams as normal.
GCSE exams start in the second week of May and run until mid-June.
Mr Barton said many head teachers were facing questions about the exam season, and there was an urgent need for reassurance.
"Parents and pupils are worried about being the victim of something out of their control and are asking, 'Will I get into college or university?'"
Mr Williamson said: "We're doing everything we can to make sure it's fair for students, we're having regular discussions with Ofqual."
The government warned on Thursday that within weeks, whole households would be asked to self-isolate if one person showed symptoms consistent with coronavirus.
It is not clear exactly what this would mean for a teenager unable to sit their exams, but there are mechanisms for allocating marks in exceptional circumstances, which have been used before.
The Welsh government has been advised that school closures are not an appropriate move at the moment, though the situation remains under review.
The Scottish government has also said school closures would not be an effective measure at this stage.
The Republic of Ireland's decision to close schools, colleges and public childcare facilities until 29 March is likely to affect businesses in Northern Ireland's border region that employ staff from the Irish Republic.
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Coronavirus: Government insists schools should stay open - BBC News
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