London: The government has said all pupils, in all year groups, in England will be expected to return to class full-time in September.
Schools have already reopened in Scotland.
Prof Whitty, who is also England's chief medical officer, said "many more [children] were likely to be harmed by not going than harmed by going" to school.
"There's also very clear evidence from the UK and around the world that children much less commonly get a severe illness and end up having to be hospitalized if they get symptomatic Covid," he added.
His interview came as chief and deputy chief medical officers for all four UK nations said there were "no risk-free options" and it was important for parents and teachers to understand both the risks and benefits as schools reopen.
Children are more likely to be harmed by not returning to school next month than if they catch coronavirus, the UK's chief medical adviser says.
Prof Chris Whitty said "the chances of children dying from Covid-19 are incredibly small" - but missing lessons "damages children in the long run".
Millions of pupils in England, Wales and Northern Ireland are due to return to school within weeks.
Prof Whitty also said Covid-19 would be a challenge for at least nine months.
He said it was unlikely there would be a vaccine in 2020 but there was a "reasonable chance" of a successful jab being ready for the following winter in 2021-22.