How do you, or your children, wear their school uniform?

I have 2 daughters, dd1 is 15 and in year 10 and dd2 is 13 and in year 8. They are normally well behaved girls, but at the moment I am having serious trouble in getting them to wear there school uniform properly and neatly. Both dds wear their ties very short and with a big knot, and undo the top 2 buttons on their shirt. They are supposed to wear a jumper, but dd1 never wears hers and when dd2 wears it, she pulls the collar really wide and the tie is barely visible over the jumper. They also both wear really short shirts to school and roll them up when they leave the house, and ive given up trying to tell them to wear uniform properly. I understand they want to look cool and I could cope with them untucking there shirts, but both dds keep gettiing after school detentions for bad uniform. They say that all of their friends wear their uniform in the same way, but if everyone does it then why do they keep getting detention??? Just wondering if anyone has had similar experiences and hassles over uniform with their daughters/sons? and if u have, did u get them to listen or did u just let them keep getting detention? Or to any kids out there, how do you wear your school uniform?