School children have been banned from playing outside during heatwaves, with a former head teacher warning kids could become "wimps".
Students have been kept inside classrooms by teachers for "hot play" breaks when playgrounds have been classed "too hot to use safely".
While the move aims to keep students away from outdoor surfaces which have roasted under the sun, critics have labelled the move "absolute nonsense".
They claim it risks the next generation being taught to "hide from warm weather".
The idea of "hot play" during heatwave events is following in the footsteps of the "wet play" which is regularly adopted when there is too much rain.
Environmental group WWF has called for schools to use natural surfaces instead of artificial ones in a bid to "mitigate" extreme weather effects.
Former Head Teacher and Campaign for Read Education Chairman Chris McGovern has warned that keeping students inside during hot weather was bad for their development.
"I taught for 35 years. Any teacher knows that the worst thing you can do on a hot day is to keep children confined into the classroom," he told The Telegraph.
Schools have kept kids inside the classrooms on breaks during heatwaves
GETTYHe admitted there were "situations where a particular child needs to stay indoors" and there should be shaded areas.
But, McGovern said "common sense" should be applied and keeping them inside was "the worst possible way forward for helping these children".
He said similarly, in cold weather, kids should be running around.
"We're making them into wimps. We don't want to make children into wimps," McGovern warned.
School playground
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"We want to toughen them up a little bit."
McGovern fears restricting children's freedom risks damaging their long-term mental health, and it was an "awful childhood we're inflicting on [them]".
He added that it encouraged kids to use their iPads or mobile phones, which is the "opposite of what we want".
Mid Buckinghamshire MP Greg Smith said the move was "absolute nonsense", adding it attempted to "wrap children in bubble wrap".
Instead, Smith believes the "correct answer" is to take precautions like wearing hats, sun cream and light clothing" instead of hiding from the warm weather.
Former Tory Cabinet minister, Sir Jacob Rees-Mogg, said he was surprised the WWF "thinks children count as wildlife".
"I am not sure the children of England are that feral," he said.
"Letting children enjoy the sunshine is only natural, and I fear these woke charities have too much time and money on their hands."
The WWF has claimed many schools have replaced natural features with heat-retaining materials, which "exacerbate the impact of high temperatures".
The charity has urged the Government to update its regulations, which they have described as "outdated".
It wants pupils to have access to natural surfaces like grass, soil and sand with no actual requirement for schools to provide this.
The charity's Director of Campaigns, Rosalind Mist, claimed climate change meant "we're facing more and more extreme weather" and schools were currently vulnerable to risks of overheating or flooding.
She said the "cheap solution" was adding more nature and natural surfaces to school grounds.