The Government has been urged to drop plans which could see all primary schools in England returning to normal before the summer holidays.
Ministers have said their five key tests required for the easing of lockdown have been met – and schools will admit more pupils in Reception, Year 1 and Year 6 from Monday.
There are hopes all pupils will then return to school four weeks before the summer break begins in July, though schools standards minister Nick Gibb has said the final decision will be led by the science.
Ms Knights has written to Education Secretary Gavin Williamson asking him to “review and drop” this expectation, according to the BBC.
She told the broadcaster: “Unless something dramatic changes very soon in terms of the Government’s scientific and medical advice, it will simply not be possible for primary schools to invite all pupils back for a whole month of education before the summer holidays.
“It is adding to uncertainty for parents, but also extra pressure on school leaders and governing boards who think that they need to try and do this when actually it wouldn’t be safe.”
Schools, colleges and nurseries closed more than nine weeks ago due to the Covid-19 outbreak, remaining open only for vulnerable youngsters and the children of key workers.
Class sizes will be limited to 15 from Monday, with Government guidance also suggesting desks should be spaced as far apart as possible.
Meanwhile, the National Education Union (NEU) said the contact tracing system must be running successfully before the risk level that comes with children and teachers returning to school can be mitigated.
“Even at this late stage, we call on the Government to draw back from wider opening of primary schools from Monday.
“Instead we urge Government to engage in talks with the profession and the unions, including the NEU, about how to open schools more widely once the contact tracing system is shown to be working.”
He wrote: “Covid-19 has made it even more difficult for some children to get the most from their education and we cannot let the virus wreck the hopes and dreams of a generation.”
A survey by the PA news agency of local authorities found more than a dozen are advising schools not to open to more pupils from Monday.