Mr Johnson is expected to announce plans for all students to return to England on March 8th when he sets a roadmap to ease the lockdown later Monday.
Aside from outdoor activities, schools that went online in early January for all but vulnerable and important working-class children will be the first to line up for a return.
Geoff Barton of the Association for School and College Leaders (ASCL) said that while his union shared the government's goal of getting all children back on the ground as soon as possible, it remained "concerned about the idea of a" big bang "approach for a complete return of students all at the same time ”.
He said it was "difficult to understand" why England's approach would "go so much further" than the plans in Scotland, Wales and Northern Ireland. who have opted for a gradual return to school.
"It is critical that all students' return to personal education is safe and sustainable and that we do not extend an interruption cycle," said Barton.
Paul Whiteman of the NAHT School Directors' Union also urged children to return to school safely and to reduce the risk of further disruptions to their education.
"A third school lockdown would be more devastating than taking your time now," he said. "The government's job today is to reassure families and professionals alike that they have a solid scientific basis for their approach and a well-thought-out plan on how to safely reopen schools to all."
The NAHT General Secretary added: "We need a careful plan for a sustainable return."
Matthew Davies, a school principal, said The independent He was "concerned" about the prospect of a fuller reopening of all students early next month.
"I was hoping to see a gradual increase in student numbers from March 8, coupled with additional measures to support school principals," he said.
Andy Byers, a secondary school principal in Durham, said he was keen to get back to school as soon as possible but was concerned about how the student testing plans would work.
The government has announced that secondary and college students will be offered coronavirus tests on their return.
"I am concerned about student testing and want to learn more as it will be impossible for many schools to test that many students in such a short time," said Byers The independent.
Ian McNeilly, the executive director of the de Ferrers Trust, which operates seven schools in Staffordshire and Derbyshire, said: “I suspect secondary schools will fluctuate student returns in the week of March 8th as it will be difficult to get through a school to come test program for students when they all return on Monday. "
Another head of the Academy Trust, Lucy Heller, told the BBC today On Monday's program, she wants a “movement for early vaccines” for frontline employees – including schools – before March 8.
Meanwhile, Labor leader Sir Keir Starmer told LBC it was "frustrating" that the government did not use half-time to vaccinate teachers and school staff.
Mr Johnson has said the roadmap – which will be announced later on Monday – would "cautiously" get England out of lockdown.
"Our priority has always been to get children back to school who we know are vital to their education and wellbeing," he tweeted Monday. "We'll also prioritize ways people can safely get together with loved ones."