Should there be some sort of dress code in school?

I totally get the unfair misogyny girls have had to endure, but right now I'm picking up my boyfriend's little sister who's in high-school and I'm not exaggerating, girls are wearing shorts with their booty cheeks out and not crop tops, but sports bra's. I'm not one to shame anyone on how they dress, I myself post spicy pictures on my Instagram, but I'm also an adult. I was talking to one of the girls in the office and she mentioned dress coding anyone is considered sexual harrasment. There was a mention in the beginning of the school year of what's not allowed, however it's not enforced do to its nature.