leverkusen - that's not been my experience at all. Totally the opposite. My kids all go to the school in the most basic, cheapest jeans I can buy, and I'll get them t-shirts from M&S, H&M, basically anywhere with 2 initials it seems.
They don't look after their clothes, roll in mud and climb tree so I won't spend loads of money at all. Not once have they been commented on. And I'd say they don't look any different from their peers. I also work in my ds school and never heard any comments. Never been aware of any clothes related bullying.
Now ds1 in secondary, he's (and therfore I'm seeing) all the older teens and not once have I seen any of the girls dressed skimpy or inapproriately. Mainly jeans and t-shirts there too, albeit skinny jeans. The boys do tend to wear their jeans at half mast though
Not a good look.
OTOH, when I return to the UK, my eyes are generally on stalks with what girls wear, esp with the girls in their uniforms. I thought my mum was exaggerating when she described the teeny minis they wore. SHe wasn't.
FFS either have a uniform or don't. If you have one, enforce it, parents and school alike. It looks so shit to see the majority of the school taking the piss with it.