I wore short trousers all the time as a child. They were part of the compulsory uniform at the junior school and outside of school that was all my mother had for me to wear as well, was the same for most of the boys I knew. I would be in shorts all year round regardless of whether. At the seniors, the shorts were also compulsory up until the third year at the age of 13 when long trousers could be worn but that wasn't compulsory on the other hand, it was at the parents discretion. Many boys started wearing long trousers at this point and it was a sort of rite of passage that showed you were older and closer to adulthood. Not all mothers got their boys longs immediately at this point though, including mine. I quickly started to dislike them as they seemed a symbol of me still being a little boy.
I was kept in shorts until I was almost 16 by which point I was one of very few of my own age that I knew of. It was embarrassing when I would be somewhere with younger boys who were in longs while I was still there in my shorts. I was glad when I finally did get a pair of long trousers. I do wear shorts these days on hot summer days though (not grey flannel ones though).
As for punishment by being put back in shorts, that definitely went on with boys in those early teenage years. Never to me though, that ship had sailed by the time I got out of them in the first place.
