A head teacher has criticised the government's plans to reopen primary schools, claiming "it's not going to be safe, and it's not going to be normal".
Addressing parents via Facebook, Debbie Whiting said social distancing "never would exist" at North Denes Primary School in Great Yarmouth, Norfolk.
Her post on the school's page has since been shared thousands of times.
The Department for Education said it wanted children to return to school "as soon as possible".
The government has said children in reception, Year 1 and Year 6 could return on 1 June, but teachers' unions have said there are still "unanswered questions about safety".
Mrs Whiting said she felt a need to be honest about "the reality of how school will be" to allow parents to choose whether to send their child.
Describing the requirements, she said trying to set up smaller teaching groups or "bubbles", enforce social distancing and carry out continuous cleaning was a "real headache".
She told parents: "I can tell you quite honestly that there is no such thing as social distancing in a school - we can try but we certainly cannot guarantee it.
"It does not exist and never would exist.
"We can always make things safer, we could perhaps reduce the risk slightly but as soon as lots of children return, I can tell you that the risk will be there."
Speaking to the BBC, she said he had been praised by parents for her honesty and other head teachers for "sticking her head above the parapet".
"I am not trying to stop people sending their children back, or make them feel guilty," she said.
"This is going to be really hard for young children - how can you tell them don't play with others, don't go near them?
"It's not going to be safe and it's not going to be normal."
She said she believed teachers would focus on children's emotional wellbeing in class and those remaining at home would not lose out.
"I would rather they fell behind in their learning a little bit and they were safe and they had the right experience," she said.
"They are not going to learn in a school in bubbles, not being allowed to go near their friends
"I think for their mental health they are better off at home."
The Department for Education said: "We want children back in schools as soon as possible because being back with their teachers and friends is so important for their education and their wellbeing."
It said the phased return was based on scientific and medical advice, and it had engaged closely with the unions and would continue to do so.