School uniform

From experience the fabric the boys short trousers are made of isn't very thick at all, hold them up to the light and you can practically see through it! Extremely poor quality in my opinion.
I don't know many boys of school age who would want to wear gingham shorts either, far too babyish.

I don't think there would be a ready market for gingham shorts amongst the boys.

Supply equals demand though. My DGS has a pair and they're very sweet. His M&S school shorts are very thick. Far too hot.

Cool!

I should have thought that any shorts are going to be cooler than long trousers just because there is so much more skin exposed and air able to circulate more easily.

Yes. Not as cool as the thin dresses girls are allowed to wear in summer tho.

Just as it was a while back, when girls had to wear skirts in winter.

I can't say I can imagine my boy in gingham shorts, though.
Simon from the inbetweeners comes to mind.

I think girls can only wear it until they're 6 or 7 ish.

My boy looks adorable in his ???

Of course he does, I'm sure.