There is little evidence of coronavirus being transmitted in schools, Education Secretary Gavin Williamson has said.
Mr Williamson said the government was being guided by the best science as it accelerated plans to reopen schools to all pupils in England next month.
Government advisers have warned the nation may have reached the limit of what can be reopened in society safely.
But Mr Williamson suggested an upcoming study would support the government's position on reopening schools.
His comments come after Prime Minister Boris Johnson said the reopening of schools - after months without in-person education - was the "national priority" of the government.
The prime minister, who visited a school in East London on Monday, is understood to have made it clear that schools should shut last in any future local lockdowns - after businesses including shops and pubs.
The current plan is for most children across the country to be back in class by next month.
Schools across the UK closed on 20 March, except to children of key workers or vulnerable children. On 1 June, they began a limited reopening for early years pupils, Reception, Year 1 and Year 6.
The Association of School and College Leaders said guidance from the government was not clear, and schools were having to make their own contingency plans for any possible resurgence of coronavirus. It said teachers might teach students on a week-on, week-off basis in that situation.
But care minister Helen Whately told BBC Breakfast: "Our priority is to make sure that children are fully back in school come the autumn."
She said the government wanted to keep schools open in the event of local lockdowns, adding that staff and pupils would "immediately have access to testing" if they showed symptoms.
Prof Russell Viner, president of the Royal College of Paediatrics and Child Health and a member of the government's Scientific Advisory Group for Emergencies (Sage), said "rota systems appear to make very little difference" to the level of risk.
In an interview on BBC Radio 4's Today programme, he said opening up schools was "one of the least risky things we can do" when it comes to easing lockdown.
By Rachel Schraer, health reporter
The evidence is clear that children are much less likely to become very ill from coronavirus than adults. What role they play in spreading the virus to others, though, is less clear.
A review of 18 studies suggested children might be half as likely as adults to pass on the virus.
But schools do not just bring children together - teachers, parents at school gates and other knock-on effects like more people on public transport or in offices could also influence the spread of the virus.
While we have not fully solved the question of whether children are biologically less capable of passing on the virus, the safety of re-opening schools depends on other factors, too.
The strength of the contact-tracing system and how well social distancing can be managed will be crucial in whether re-opening schools will cause cases to spike.
The education secretary said the "latest research, which is expected to be published later this year - one of the largest studies on the coronavirus in schools in the world", would make it "clear there is little evidence that the virus is transmitted at school".
He is believed to be referring to a forthcoming report to be released by Public Health England.
In a statement issued on Sunday evening, Mr Williamson also said there was "growing confidence among parents about their children returning" to the classroom.
"This is down to the hard work of school staff across the country who are putting in place a range of protective measures to prepare to welcome back all pupils at the start of term," he said.
'Too many questions'
But some parents have told the BBC of their concerns at the plans.
Jo, a mother of two who works as a support staff member at a secondary school in south-east England, said: "I'm terrified of sending my children back to school. I'm frightened that [those in] schools are not wearing masks, not facing desks forward."
She questioned whether head teachers would "have the courage to send home unwell children on arrival".
"At my school, we have been given a brief outline of the plans for when the school reopens, but things are changing all the time," she added.
"There are too many questions and not enough answers."
Meanwhile, Labour called for a "rapid reform" of the test and trace system, suggesting local health protection teams were more effective than national call centres.
The Mayor of Greater Manchester, Labour's Andy Burnham, told BBC Breakfast that England's contact tracing system "isn't yet good enough" for pupils to return to school in September.
He said the government must give local authorities resources to carry out some of the contract tracing and "give all employers in the country the ability [to support employees] to self-isolate on full pay".
Figures released last week by the Department of Health and Social Care showed that local teams continued to be more successful than call centre workers when it came to reaching close contacts of people who tested positive for coronavirus.
In a letter to Health Secretary Matt Hancock, shadow health secretary Jonathan Ashworth and shadow cabinet office minister Rachel Reeves raised concerns that the current model was "not fit for purpose".
On Sunday, the UK reported a further eight people had died after testing positive for coronavirus, taking the total to 46,574. A further 1,062 people tested positive for Covid-19.
In another development, gyms, swimming pools, leisure centres and children's play centres are being allowed to reopen in Wales on Monday, in a further easing of the lockdown restrictions.