At the Select Grammar I attended in the 60s, the school cap was compulsory - but it was just for the first year students! Boy you were in trouble if you were spotted off the school premises and not wearing it.That was also my experience in the 1960s, similarly at a boys Grammar School. The only hated item in the uniform was the school cap but the requirement to wear that got gradually abolished over the decade.
The other thing was tie snobbery. You started with a basic school tie, but then you were entitled to wear a differently-designed one if you won a "House Colour" (for sporting achievements). Eight Houses, so 8 differently coloured ties. And then there were different ties again for prefects and 6th Form Club Members. Very few boys finished their school career only entitled to wear the basic tie, the lowest of the low. I was one ....
I think there was a Gent's Outfitters in a nearby suburb which you had to use - they seemed to have exclusive rights to the School's uniform.