A governmental advisory body said a two-week postponement would "halve" the risk to primary and secondary school children, the ones expected to return to school first.
Reopening UK schools on June 1 is too early, according to UK's Scientific Advisory Group for Emergencies (SAGE).
A two-week postponement would instead "halve" the health risk to children and also "allow greater time to set up an effective test, trace and isolate programme in all areas", the independent governmental advisory body said.
SAGE outlined its proposal in a draft report published on Friday, May 22.
The report reads: "We believe that decisions on school opening should be guided by evidence of low levels of COVID-19 infections in the community and the ability to rapidly respond to new infections through a local test, track and isolate strategy. There is no clear evidence that these conditions are met. Until they are it is not safe to open schools on June 1".
The report also says that local innovation is required to provide educational opportunities for all children, with suggestions including requisitioning of community facilities, sports clubs, school playing fields, and football stadiums for use by schools.
UK Education Secretary Gavin Williamson said on May 16 that primary school children in reception, year 1 and 6 - as well as secondary school pupils in years 10 and 12, would be those returning to school first, but in smaller classes.
Williamson said children will be kept within those smaller groups, while schools will also see "rigorous" standards around hygiene and cleaning.
"This includes reducing class sizes, making sure pupils stay within these small groups, creating a protective and small bubble around them", he said.
Spokesman for British teaching union NASUWT Simon Kennedy said on Thursday that reopening "has to be done securely, it has to be done safely. You know the medical evidence from SAGE is only being produced today. Schools won't have had time to analyse that to actually determine whether or not the risk assessments that they are putting in place are sufficient to protect the children and the teachers and until that happens we don't think schools should open."
SAGE held a public consultation on Friday, May 22, in partnership with the British Medical Journal and Mumsnet, taking questions from the public that will feed into a final report due to be presented to the Government next week.
The event was live-streamed on SAGE's YouTube channel.