School uniform rules should be reviewed to avoid pupils getting cold in classrooms where windows have been opened to combat the spread of Covid, schools have been told.

Schools should let pupils “dress accordingly” if they are aware that classrooms are colder, the Department for Education has said in a new blog.

However, it has also insisted that keeping classrooms well ventilated by opening windows does not mean they have to be cold.

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The DfE said that partially opening windows - or opening them for a short period - can still improve ventilation.

And it suggests doing this at times when the classroom is empty.

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The DfE blog says: “Schools should let pupils dress accordingly if they are aware classrooms are cooler than usual.

“Uniform rules should be reviewed to make sure all pupils can dress suitably at all times.”

It adds: “Only opening windows for 10 minutes an hour can help reduce the risk from virus in the air - and, where possible, this can happen when the room is empty in the periods between lessons, for example.

“Where this isn’t an option, opening higher up windows or vents causes fewer draughts, as does opening other windows by a small amount. Opening the doors to classrooms helps, too.”

The DfE has delivered more than 353,000 carbon-dioxide monitors to schools.

The department said this has enabled staff to identify areas where ventilation needs to be improved and has provided reassurance that existing ventilation measures are working.

The DfE has also provided 1,000 air cleaning units to special schools and alternative provision settings, and allowed all state schools to bid for another 7,000 units providing they meet the government’s criteria.

Answering MPs’ questions last week, education secretary Nadhim Zahawi said that providing more filters than were needed would be a “waste” of “taxpayers’ money”.

Schools minister Robin Walker made similar comments today when appearing before the Commons Education Select Committee.

He said: “It is not the case that there are 350,000 classrooms out there which are desperately in need of these devices and would benefit from them.”

Schools could only apply for an air cleaning unit if classrooms record sustained high CO2 readings for at least a week despite taking all possible measures to improve ventilation - such as opening a window.

They also need to be able to demonstrate that building work needed to improve ventilation could not be completed by the end of next month.