To see the UK’s failure to plan for the impacts of climate crisis, look no further than Beaconsfield primary school in west London – where a building more than 100 years old copes with extreme temperatures better than its neighbour, built less than 10 years ago.

“I’ve got two buildings on my site – the older building is a Victorian-Edwardian-style building. It’s roughly 130 years old. That building is constructed with solid brickwork, very thick walls. It stays warm in winter and in summer it tends to keep the heat out so it is cooler inside. Even this week it’s starting to get uncomfortable but it’s still tolerable,” said Dave Woods, Beaconsfield’s headteacher.

“The school’s newer building was constructed in 2017, following the Department for Education’s (DfE) building design guidance in place then, and it’s extremely hot all the time. Even before the peak of the heat arrived we’ve already had classes using empty spaces in the older building just so they could get some respite.”

Woods began his teaching career in Sydney, Australia, where schools have long been designed with high temperatures in mind, allowing them to stay open in scorching weather similar to that being experienced across England and Wales this week.

Although some of the schools hit hardest this week date from the 1970s, with long flat roofs, inadequate windows and little thought given to orientation, others are much more modern – designed and built in the 2000s, as the dangers of a heating climate were recognised.

Even the vaunted Building Schools for the Future plan initiated by Tony Blair, which was meant to replace Victorian-era state school estates with inspirational modern architecture, lacked basic requirements that could have mitigated the predictable impacts of the climate crisis.

“I know a colleague a few suburbs away from me who described a school with enclosed glass walkways, an enclosed fully glass atrium, a glass canopy over the top of their dining room, and a whole glazed side of the PE hall that is south facing. Basically it’s a school that has been set up as a greenhouse,” said Woods, the current president of the National Association of Head Teachers.

Successive governments have failed to tackle the worrying proportion of school buildings that remain in use long past their predicted lifespan, with many riddled with asbestos and crumbling concrete.

And it’s not just schools. Despite more than two decades of warnings and government promises to act, the UK is still damagingly unprepared for the impacts of the climate crisis, according to the Climate Change Committee (CCC), the government’s statutory advisers.

In a recent report the committee found all the plans made so far for adapting to extreme weather to be “not fit for purpose”. The committee highlighted education as a particular problem area and called for all schools to be fitted with air conditioning, but gave ministers until 2050 to do so. The government does not have to accept this recommendation.

Another measure the CCC offered was to reconsider the school year due to high classroom temperatures and students’ inability to sleep well at night. Only longstanding tradition mandates that exams should happen in May and June.

In England the DfE is looking to accelerate its school refurbishment programme. Last year it announced almost £20bn investment in its school rebuilding programme through to 2035 to overhaul more than 750 schools and sixth-form colleges. It has also started a new “renewal and retrofit” programme worth £710m for schools and colleges to increase resilience to climate change by 2030.

But with more than 22,000 state schools and colleges, ensuring they are all fit for a hotter future will take billions more, when time is running out.

Dr Thomas Roberts, senior lecturer in environmental sociology and weather health researcher at the University of Surrey, said: “Climate adaptation is no longer something we need to prepare for in the future. It is something we need to be doing now.”