By barring particular outfits from school, dress codes help boys identify and objectify “inappropriate” girls and women. Girls who violate dress codes are violating rules, and girls who violate rules are bad. Bad girls can be desirable and sexy, but they don’t necessarily deserve respect (even from other girls).
And where respect is absent, objectification is easy. In her guide to self-objectification, Caroline Heldman explains how sexually objectified women are dehumanized and viewed as “less competent and worthy of empathy by both men and women.” Those who are dehumanized may be mistreated and made to feel inadequate. And if poor self-image is linked with objectification, it isn’t hard to see that this cycle feeds itself: Those who are objectified by others are treated as less than human, and in understanding themselves as less than human may self-objectify.
Asking girls to cover up is a Band-Aid solution to far more socially ingrained problems such as general misogyny and rape culture. As long as a girl or woman is always sexualized, it won’t matter how much she covers up—she’ll still be faulted for her inappropriate behavior.