How come white girls can wear reviling clothe but everyone else cant ?

i no I'm a guy but i live in Arlington(where the pentagon is) i go to a school called Yorktown. The white girls at my school always go to school in shorts and every time a Hispanic girls wears something like that they get in trouble. Today a black girl got in trouble for wearing shorts that were to short and she asked the teacher why the white girls get to wear shorts and the teacher said its because white girls have no curves