My dd1 (6 today!) doesn't give a monkey's about clothes, but a few of the girls in her class are more interested. Haven't seen much to shock me, more an overabundance of pink so far - but one girl came to their non-uniform day last year (P1) in a boob tube which I found a bit iffy.
I find that clothes from Next aren't too alarming and dd1 is happy in jeans and T-shirts, so we're doing OK so far. I dread to think what it will be like when she's older, though - and I suspect that dd2 will be starting rather sooner. People already give my dd1 makeup, etc, as presents - dd1 isn't interested but dd2 is fascinated by it already.