The return of all students for face-to-face learning for the first time in 2021 is the initial step in Prime Minister Boris Johnson's proposed roadmap out of lockdown for England.
Department for Education figures reveal just 13% of pupils were being taught on site at schools in Buckinghamshire in the latest snapshot assessment of attendance taken on February 11.
However, that was up from the 11% who were estimated to be in the area's schools a month earlier.
The attendance rate at primary schools was higher, at 21%, compared to 4% in secondary schools.
The latest figures are based on responses to a survey from 84% of Buckinghamshire's state-funded schools.
Pupils in schools and colleges in England, except children of key workers and vulnerable pupils, have been learning remotely since the start of the lockdown.
Around 16% of students across the country attended school in the week before half term, but this rose to 18% last week following Mr Johnson's roadmap announcement.
Geoff Barton, general secretary of the Association of School and College Leaders, said the number of children being educated on site has been "much higher" than during the first lockdown at many schools.
"It has been extremely unhelpful that the Government has at no point clarified whether there is a safe limit," he added.
“Schools are now focused on the task of reopening to all pupils from March 8. They are very much looking forward to welcoming back all children.
“However, this has been made more challenging for secondary schools by the lack of clear direction from the Government over the use of face coverings in classrooms, as well as the huge logistical exercise of running Covid testing stations."
The data from the February 11 assessment also shows the availability of education staff.
In Buckinghamshire, only 5% of teachers and school leaders were unable to teach on site or remotely on February 11. Just a fraction were off for Covid-related reasons.
Education Secretary Gavin Williamson said: "Everyone working in schools and colleges has been going to extraordinary lengths over the past weeks and months to continue educating our young people, providing care for vulnerable children and juggling the demands of having some children in school while most receive their education remotely."
He added that the DfE will introduce extra safety measures, including asking secondary school students to wear face coverings in classrooms and providing twice-weekly rapid testing for students and their families.
Mr Williamson said the measures "should provide extra reassurance that we are taking every opportunity to reduce transmission of the virus and keep everyone safe".
However, the National Education Union has criticised the Government's plan to open all schools in England on March 8, which differs from the "cautious, phased" approach being taken in Wales, Scotland and Northern Ireland.
The union's joint general secretary Dr Mary Bousted said: “A ‘big bang’ school reopening brings 10 million people back into crowded buildings with no social distancing and inadequate ventilation.
"The wearing of face masks by pupils and staff in in secondary school lessons is a welcome measure but it is not, on its own, enough."