So many people missing the point.
Yes children do go to school in hotter places, but they are used to the higher temps and the temps usually rise gradually.
The UK is not equiped for the higher temps and it is a significant increase in temp over a short period of time.
In UK school, if you are lucky, there maybe one fan per class, that's only going to help the lucky 4 people sat nearest to it.
Windows do not open fully. They let in no breeze.
You can't have the doors open because of the noise and many are fire safety doors.
There are upto 40 people in the class, this raises the temp even more.
The children are hot, sticky and uncomfortable, they are grumpy and no learning gets done.
They will all be sent outside at breaks and there will not be enough shade outside for everyone.
Children are easily affected by heat, especially the younger ones. You send more time dealing with children complaining they feel, sick, dizzy etc than you do teaching.
Some of them will turn up in unsuitable clothing, with no sunhats or suncream.
It's bloody miserable for everyone.
Best things I did was tinfoil the windows.
Put the tinfoil on cardboard (shiny side facing out) and attached the cardboard to the outside of the windows. This stops the heating hitting the glass and significantly lowers the temperature inside.
You can attach the tinfoil to the window on the inside, but it won't be as affective.
Good luck op, I feel your pain.