Boris Johnson has issued a personal plea to parents to send their children back to the classroom when schools reopen in September.
The Prime Minister said the risk of contracting coronavirus in schools is "very small" and pupils face greater harm by continuing to stay away from the classroom.
He said it was the Government's "moral duty" to reopen the schools as he stressed that authorities now know more about Covid-19 than they did when the country went into lockdown on March 23.
"I have previously spoken about the moral duty to reopen schools to all pupils safely, and I would like to thank the school staff who have spent the summer months making classrooms Covid-secure in preparation for a full return in September," Mr Johnson said.
"We have always been guided by our scientific and medical experts, and we now know far more about coronavirus than we did earlier this year.
"As the Chief Medical Officer has said, the risk of contracting Covid-19 in school is very small and it is far more damaging for a child’s development and their health and wellbeing to be away from school any longer.
"This is why it’s vitally important that we get our children back into the classroom to learn and to be with their friends.
"Nothing will have a greater effect on the life chances of our children than returning to school."
Many pupils in England have not been to class since March when schools were closed, except to look after vulnerable children and those of keyworkers.
Schools in Scotland reopened earlier this month, while those in England, Wales and Northern Ireland are expected to welcome all pupils from the beginning of September.
Mr Johnson's comments come after the UK’s chief medical officers issued a joint statement seeking to reassure parents that it was safe to send their children back to school.
They said "very few, if any" children and teenagers would come to long-term harm from the virus solely by attending school, while there was a “certainty” of harm from not returning.
Liberal Democrat education spokeswoman Layla Moran said: "The Government must rapidly upscale Test and Trace and ensure schools have the mental health support, financial resources and the use of community spaces they need ahead of opening fully.
"The country, and seemingly the Prime Minister, has lost faith in Gavin Williamson. To restore confidence among parents, pupils and teachers the best thing the Prime Minister could do is sack him, rather than speak for him."
It comes as analysis found there were 30 outbreaks of coronavirus in schools in England after they reopened.
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A Public Health England report, published on Sunday, said the reopening of schools following the easing of national lockdown was associated with a total of 198 confirmed Covid-19 cases, 70 in children and 128 in staff.
There were 67 single confirmed cases, four "co-primary" cases and 30 outbreaks of Covid-19 in schools during June, it added.
A total of 121 cases were linked to the outbreaks, 30 in children and 91 in staff, the analysis said.
The report said there was a "strong correlation" between community coronavirus incidence and risk of outbreaks in educational settings, even during a period of low Covid-19 incidence.
But it added this was not surprising because increased community transmission provided more opportunities for the virus to be introduced into educational settings.
The report said: "The potential for spread within educational settings, as observed from the wider swabbing of some schools in our surveillance and from recent reports from other countries, does suggest that school closures may be necessary as part of lockdown in regions with increasing community infection, although given what is known about the detrimental effects of lack of access to education on child development, these should probably be considered only in extremis by comparison with other lockdown measures."
Education settings in England were asked to reopen to children in nursery, Reception, Year 1 and Year 6 at the start of June, extending to Year 10 and 12 students from June 15, the analysis said.
But it said the reopening was not mandatory and was met with "mixed responses", with only 1.6 million of the 8.9 million pupils nationally attending any educational setting during the "summer mini-term".
Kevin Courtney, joint general secretary, of the National Education Union, said schools and colleges needed to know what should happen if an outbreak of the virus occurs in individual schools or through national, regional or local spikes.
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He said the Government needed to issue guidance on moving to teaching rotas or limited openings and to hire more teachers to allow education to continue if infection rates rise.
"Government advice needs to cover the possible self-isolation of bubbles and, in extremis, moving to rotas or to more limited opening," Mr Courtney said.
"It needs to cover advice to heads about the protections needed for staff in high-risk categories if infection rates rise.
"Government should be employing more teachers and seeking extra teaching spaces to allow education to continue in a Covid-secure manner if infections rise."