Oh, Kali, that's almost exactly the situation I was in! I was raised Catholic and at my private school we had to wear our skirts to our knees- I'm not even sure if girls were allowed to wear pants! Pretty much the closest thing you could get to a uniform without it actually being one. At any rate, I don't remember ever wearing pants to school in elementary school. Now in college I can wear whatever I damn please- on the first day of school I wore a miniskirt that damn near showed my undies when I bent over!
