Teachers could refuse to return to school if they do not believe it is safe to do so, it is understood.
Government officials have reportedly made provisional plans to reopen schools for Year 6 pupils on June 1, although no official announcement has been made yet.
However, unions may tell teachers they have the right to stay away from schools if they do not think it is safe, reports say.
Eduction unions will not be allowed to encourage members of the profession to stay at home if schools reopen against their wishes, according to the i newspaper.
If the groups did this they could be accused of potentially backing illegal strikes.
However, it is understood they could inform teachers of their rights under Section 44 of the Employment Rights Act 1996, which allows employees to stay away from unsafe workplaces.
A spokesperson for the Department for Education told inews: “Education Secretary Gavin Williamson has not set a date for schools reopening.
“Schools will remain closed, except for children of critical workers and vulnerable children, until the scientific advice indicates it is the right time to re-open and the five tests set out by Government to beat this virus have been met.
“We are also working closely with the sector as we consider how to reopen schools, nurseries and colleges and will ensure everyone has sufficient notice to plan and prepare.”
Education Secretary Gavin Williamson has said he wants to see children returning to school "when it's the right time" based on the scientific and medical advice.
Mr Williamson added that there would be a "phased approach" to reopening schools.
However, newly appointed shadow education secretary Rebecca Long-Bailey warned that parents are "anxious" about sending their children back to school.
Ms Long-Bailey asked Mr Williamson during education questions on what basis the Government would take the decision to reopen schools.
Mr Williamson replied: "In terms of the return of schools, obviously she, I'm sure, shares with me a desire to see children being in the opportunity of returning to school when it is the right time to do so.
"This will be based on the scientific and medical advice that we receive.
"What I can assure her is that we will take a phased approach in terms of reopening schools and we will always aim to give schools, parents and, of course, critically importantly, children the maximum notice in terms of when this is going to happen."
