When I say 'allowed', that's not strictly true. The school had a very long and detailed uniform list. It even specified the colour and fabric of our PE knickers.
We were meant to wear A-line knee-length skirts in charcoal grey gabardine and either a V neck long sleeved jumper or cardigan in the same colour from the two official school outfitters.
In practice we learned that any shade of grey or style would do - within reason. There was a fashion then for pencil skirts, so most girls wore skirts with side, front or back slits or kick pleats. So long as the slit didn't go up to your crotch, teachers would ignore it. I imagine I gave them a good laugh the day I turned up in a skirt that I'd taken in so dramatically I waddled like a penguin.
A skirt from Etam or a jumper from M&S - there was a craze for M&S grey V-necks in my school
- were cheaper than items from the official shops. Interestingly, it was the divide between the official outfitters that created the money/class tensions.
Both were expensive, but one more than the other. The tell tale was the blouse, which we all had to wear without question. The posher shop used better buttons - they were like little round pills. The other shop used cheaper flat ones. Their shade of pink candy stripe was harsher than the posh ones. Even though the cheaper outfitters was on my doorstep we'd go on an hour's bus ride to the other one because my mum thought it was better and I wanted to fit in.
No particular reason for my ramble down memory lane, except to say that teenagers can easily work out what's desirable from what's not and that I think I was very lucky to mostly have teachers with a sense that letting teenagers rebel in small ways is better than constantly wasting time on petty infringements of the rules.