im sorry but why do dress codes have the stupidest rules?

i go to an alternative school and its 80 degrees out right now and summer is coming fast, so how come we arent allowed to wear tank tops when its hot? the reference picture for the dress code is quite literally a gym uniform. girl summer clothing isnt like that, girl shorts are super long unless you want them. tshirts in the heat become so sweaty and sticky so why cant i wear a tank top to deal with the heat? 

i dont understand why shoulders are such a big deal when everyone has them? why are my shoulders distracting you from teaching? im wearing a tank top and jorts and ive went up to some guy friends i have and they all said its not distracting. i barely have boobs but yes i obviously wear a bra, and with a tank top you can see some bra strap. why is that a problem? would you rather me not wear one? i came across another girl earlier wearing a shorter top then me but she wasnt asked to change. yesterday i saw another girl wearing a sports bra as a shirt. non of that stuff is distracting unless you think girl clothing is slutty WHICH IT ISNT. im always finding new ways to protest the dress code because it is crazy how we are forced to cover up in such heat. 

just now, i walked into my math class and as soon as he saw my tank top he sent me out of the class to go change. why are you, an older(like 40+ y/o), distracted by my shoulders? no other male teacher, or female teacher, have said anything at all. for years females have been told to cover up so we dont distract boys, but why arent we educating them instead? 

if you know any ways to protest the sexism in the dress code please let me know