My school has no dress code, besides not allowing offensive clothing. We have chicks with more cleavage showing then you could care to see and short shorts by the dozen.
It seems my school doesn't bother with stuff like that. Ontop of no dresscode, there's a pit about 20 meters away from the school on the side behind some trees which is the lunchtime destination for pot heads, the school knows full well and rather then wasting time and energy fighting a pointless battle with teenagers and their weed, they don't care. Even with that the school is very, very nice. No vandalism whatsoever, no physical bullying at all, very little verbally too. Everything is in good condition and we have very low failure rates. Awesome highschool.