Primary teachers have been told they should be “concentrating on the teaching” after some schools went against Government guidance to advise the youngest pupils to wear masks in the classroom.

England’s deputy chief medical officer Professor Jonathan Van-Tam said on Friday that the prospect of ensuring dozens of five-year-olds kept wearing their masks was a “daunting” one.

Dr Susan Hopkin, a senior medical adviser at Public Health England, said the “strong recommendation” from experts was they should not wear face coverings and warned it could damage their language development.

With schools set to reopen in England on March 8, only secondary school students are being advised to wear masks when social distancing cannot be maintained.

But some primaries, including Selsdon Primary School in Croydon, south London, said pupils must wear face coverings at all times, except during sports lessons or when eating or drinking.

Dr Susan Hopkins, a senior medical adviser at Public Health England, told a Downing Street press conference that the “strong recommendation” of education and health experts is for primary school children not to wear masks.

She said they can have difficulty keeping them and it is “really important that they can see facial expressions in order to develop their communication and language skills”, while they have lower rates of infection.

Professor Van-Tam added: “My perspective on this is more parental than it is technical and that is to say I find it quite a daunting proposition to try and keep face masks on 30 five-year-olds in the same room.

“I just think you should be concentrating on the teaching.”

Selsdon Primary School explained its decision in a statement.

“This decision was solely based on keeping our staff, pupils and their families safe in the current situation,” it read.

But the Department for Education said primary school children should not be asked to wear masks.

Government scientific adviser Professor Calum Semple said that keeping windows open and improving ventilation in schools is much more effective at reducing coronavirus transmission than asking children to wear face masks.

Primary school children are the lowest risk both to themselves and to society.

The member of the Scientific Advisory Group for Emergencies (Sage) told BBC Radio 4’s Today programme that he is “not a fan” of asking young children to wear masks, and there are better strategies for managing the virus.

Prof Semple, speaking in a personal capacity, said: “Primary school children are the lowest risk both to themselves and to society.

“There is really good data coming out … that shows that children are half as likely to acquire the virus to a third as likely to acquire the virus.

“When it comes to transmitting, they are probably half as likely to transmit it as adults. That risk actually gets smaller as you go into younger age groups. So I am not a great fan of young children wearing face masks.”

He said he agrees that young children will find it difficult to wear the masks properly.

He added: “If I had to invest in a single activity to improve the environment both for the children and the adults, I’d be looking at improving the ventilation, unsealing windows that have been painted shut and kept shut for energy-saving reasons … improving air exchanges.

“That would be a much more effective way to reduce transmission in schools.”

Asked about the risk to teachers, Prof Semple said the data shows that teachers going to school “as a workplace are no more at risk than people in general society going about their daily living and normal working environment”.

A Department for Education spokesman said: “Children in primary schools should not be asked to wear face coverings when they return to school from March 8.

“Our guidance is clear – face coverings are only necessary for pupils in year 7 and above.”