Im curious to k now why when it comes to girl schools who have a school uniform the gorls are required to wear those uniform only during schools hours. Once off school premises they are no longer required to wear those uniform. However by bochrim, if they are caught wearing any color shirt when they are away from yeshiva , they get called into the rosh yeshivas office for a nice shmooze. No im not talking when playing sports or bain hazmanim.
Girls’ uniforms serve a different purpose than boys’ unforms. They are mostly designed to decrease the jealousy and comparisons between one girl’s clothing and another.
The purpose of the boys’ “uniforms” is mostly identification with a certain type of ben Torah. That same purpose is achieved for girls with the unofficial “uniform” of a Bais Yaakov girl – a certain level of tznius and refinement which is expected to be maintained even when not in school.