I last wore shorts when I was ten years old and if hadn't been for my mother I'd have stopped earlier
I came home from my first day in 6th class at a new school when I was about 11 and insisted that all the boys had long pants (not quite true) and as the tallest boy in the class I looked ridiculous in shorts (absolutely true). In those days a school uniform was worn especially at private schools, it was no small expense for my parents at that time.
IMHO, other than at the beach etc., shorts should only be worn with long socks and shoes. Actually in the hight of summer here in Italy many wear shorts and sandals. Working in the motorcycle shop selling spare parts I certainly did, the heat would have been unbearable otherwise.