Spite the System
Not very impressive but at my high school we had to wear a buttondown and a tie to class every day. One of the kids realized that they never specified what kind of buttondown it had to be so he wore a hawaiian shirt to class with a tie. Technically it met the dress code so it stuck.
Pretty soon most of the school started wearing hawaiian shirts with ties to class. We looked like a bunch of ridiculous Jimmy-Buffet-goes-Mormon types but it was worth it to spite the system. They changed the rule to ban hawaiian shirts a week later.
Story credit: Reddit / alagsa