I'm from the UK and when I went to school communal showers was the only option after some sport in secondary school in the 80's if you were all muddy or got wet then all boys went in the showers, the boys showers were open plan but the girls had curtains but we used both changing rooms, you didn't get privacy using the girls changing room as you had four or five boys using each shower head, the same as in the boys so we were all squashed together and you always showered with your closest friends, you had to be close as you couldn't help but be touching each other. There weren't towel hooks in the shower area so you walked to and from the showers naked.
Through the course of secondary school you all grew up together.I hear nowadays boys all wear boxer shorts when showering at schools.
I've used showers at public swimming pools but most shower wearing their swimwear, I do too, if everyone went naked as the norm then I suppose I would but as swimming pools have all ages there I wouldn't feel comfortable being naked , I've seen the occasional older guy showering naked and they are always the guys who wore speedos to swim, but younger guys, post puberty keep their shorts on, an adult section and under 18's section may be better but that won't happen as I will explain in my next paragraph.
When replacement swimming pools are built nowadays, the inevitable changing village is included with both male and females changing in the same area, in cubicles, and either individual showers or communal showers, communal showers were not a good idea as does anybody really want to shower with the opposite sex? Obviously, naked is not an option; although I didn't go naked at the male changing room only swimming pool, I was at least able to wash the chlorine off my bum, dick and balls by untying my shorts and getting my hands down there and give everything a good lathering. Also I could pull my shorts out and lett the shower wash my bits and finally putting a towel on, taking off my shorts and give them a wash, fine to do with only other males there but not something to be done with females present.