What do you think of school dress code?

I graduted High School in 2014 but when I was in High School the school dress code was very strict 3 inches above the knee, no tank top, no v-neck. I was in cross country team that our uniform was short and thick tank top, we weren't even allow to wear it during school even tho it was school issue uniform. Whoever break the rule would send to ISS with permanant record! But the rule is only aiming toward girls with the reason"Boys cannot focus in class" so they would send girls to ISS for boys to enhance they education? Now that we just got a new principal who changed the dress code rule to even stricter! Skirt has to be knee length, no legging, no yoga pant, no tank top, no shorts, no crops top, no athletic clothing and more! I have a little sister who still in high school. It's concern me.