Despite this, the Education Secretary has urged parents to send children to school if they remain open, warning “every day of absence and lesson missed has a cost”.

It comes as forecasters said temperatures could hit 40°C on Wednesday and Thursday in some spots, with a red warning from the Met Office for extreme heat.

This covers an area stretching from London to Swansea and Somerset to Birmingham, as well as in Brighton, Portsmouth and Southampton.

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Hundreds of schools have made decisions to either close completely, send children home early or make other adjustments such as relaxing uniform rules to help keep students and staff safe and comfortable.

A series of fundraisers has also been launched by parents in London, Berkshire, Cambridgeshire, Buckinghamshire and Cumbria to buy air conditioning units and fans for their children’s schools.

Bridget Phillipson said: “I know hot weather can be a struggle. But my message to families is simple: if your child’s school is open, you should keep sending them into school.

“Teachers are relaxing uniform rules, keeping classrooms cool, making sure children are hydrated, teaching critical skills like water safety, and avoiding vigorous activity on the hottest days.

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“If your child has medical needs, which mean you’re especially worried about the heat, talk to your school about what they can do.

“Every day of absence and lesson missed has a cost – and that cost falls hardest on our most disadvantaged pupils and working-class communities. So, pack a water bottle, put on the sunscreen, and trust that your child’s school has got this.”

More than 100 schools will be at least partly closed over the next days in Bristol, Gloucestershire, Oxfordshire, Buckinghamshire and Hampshire.

In Somerset, more than 200 schools will be shut or operating on more limited opening hours.

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Pupils will also either not be able to attend school or head home earlier than usual at settings in London, Essex, East Sussex, West Berkshire, Devon, Worcestershire and Herefordshire.

Many schools have explicitly cited red weather warnings and extreme heat for the reasons behind closures, with some explaining that classrooms lack air conditioning and that travel to and from school could be risky in the high temperatures.

Parkfield School in Taunton said: “Such exceptionally high temperatures present significant challenges in maintaining a safe and comfortable learning environment, particularly during the hottest parts of the day.

“Despite exploring all available options to remain open safely, we believe that the anticipated conditions will make it increasingly difficult to ensure the well-being, comfort and safety of both pupils and staff throughout the school day.

“While every school must make decisions based on its own circumstances, we believe that closing for these two days is the most responsible course of action.”

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Many pupils are set to receive work during closure periods, while many schools have offered provision for students who cannot work at home or whose parents cannot collect them early.

One parent teacher association has raised more than £3,500 in 16 hours to buy portable air conditioning units, fans and playground gazebos for Dulwich Hamlet Junior School in south London.

The organisers said: “This is an urgent and unbudgeted expense that would have an immediate impact and improve the learning environment in the summers to come.”

Meanwhile, more than 11,500 people have signed an online petition calling for a maximum temperature at which schools can remain open to be established.

Teachers’ union NASUWT has previously also urged a legally enforceable maximum classroom temperature to be set.

Chiltern Railways has warned passengers that its advise for travelling in the extreme weather conditions has been extended to Friday, June 26.

‘Significant disruption’ is expected to continue as train services are cut by half on some routes, due to temperatures up to 36C causing damaging to rail infrastructure.

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A red weather warning was issued by the Met Office from 9am on Wednesday until 11.59pm on Thursday, June 25, along with advise that temperatures could reach 40C in some places.

Chiltern Railways is asking customers not to travel unless absolutely necessary.

Michael Stewart, commercial and customer strategy director at Chiltern Railways, said: “This week’s extreme weather is going to continue into Friday so as a result we strongly advise you to avoid travelling until the weekend.

“Trains are running at greatly reduced levels as there is a significant risk to infrastructure.

“Running a reduced service means there is more resilience in the network and more chance for the rail network to recover.

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“Trains which do run may experience significant delays and see very busy conditions.

“If you do need to travel, please stay safe, check your journeys on the morning you travel as planners are still being updated and carry a bottle of water with you at all times.”

Customers who hold tickets for trains on Wednesday, Thursday or Friday this week will be able to use them on Saturday, June 27 or Sunday, June 28 instead, or are eligible for a full refund.

The actor, best known for his roles in the ITV comedy-drama Boon and Coronation Street, died on April 30.

News of his passing was shared publicly over the weekend, though his family did not disclose a cause of death.

A letter of administration, approved by the High Court earlier this month, revealed that Mr Daker’s estate was worth £306,787, reduced to £303,184 after liabilities were settled.

He left his assets to his second wife, Hilary, while his daughter, Rebecca, inherited his share of a £350,000 home in Winchcombe, Gloucestershire.

Born Colin David Daker in Bilston, Staffordshire, in September 1935, Mr Daker was best known for playing Harry Crawford, the friend of Michael Elphick’s Ken Boon, in the popular series Boon, which aired from 1986 to 1995.

He also appeared on Coronation Street as Basil Griffin between 1968 and 1969 and later as Gordon Lewis from 1981 to 1985.

Tributes have poured in from fans, one fan posted: “RIP the never-less-than-splendid David Daker,” while another wrote: “RIP.

“Thank you for entertaining us.

“Loved Boon.”

A supporter said: “Great actor who brightened up any role he played.

“I especially loved him in Boon, his partnership with Michael Elphick was great.”

Mr Daker’s television career began in 1967 with the role of PC Owen Culshaw in the BBC police drama Z Cars, where he appeared in more than 80 episodes.

He later played roles in Doctor Who, including Irongron in The Time Warrior and Captain Rigg in Nightmare of Eden, and also appeared in Porridge as Jarvis in 1977.

He went on to play Tommy Mackay in Only Fools and Horses during the 1980s.

After leaving school, David trained as a draughtsman before he quit after two years and joined the Oxford Playhouse Theatre School.

He then did national service in the Royal Air Force before he joined Oldham Rep in 1957 as a stage manager, actor, and director, and then The Royal Shakespeare Company in 1976.

David married Stella Newton in 1957, but they later divorced.

The pair had a son named Tim and a daughter called Pippa, but she lost her battle with multiple sclerosis in 1997.

David is survived by Hilary, Rebecca, Tim, and his sister, Hazel.

What character played by David Daker was your favourite? Let us know in the comments below.