When I was high school (1967-1971), the dress code at my school prohibited blue jeans. While I didn’t mind the restriction that much at the time, I know that many of my classmates longed for greater freedom and what they could wear.
A couple years after graduation, I returned to the school to visit my former band director. By then the dress code had changed and every student I saw at the school was wearing blue jeans. It was almost as if the written code had been replaced with an unwritten one that necessitated jeans.