One really obvious step in the right direction would be for schools to stop talking about what pupils wear: no uniforms, no guidelines, no rules about appearance. They could put all the time and energy they waste policing people's hairstyle choices, shoe logos, etc, into teaching kids not to be sexist and abusive.
I think that teachers lowering themselves to be concerned about skirt length/ makeup/ hair dye/ etc, sets an appalling example to students. Teachers should be concerned with helping kids to be kind and compassionate, and above all with inspiring kids to be excited about learning.
Countries without uniform, like the Netherlands and Germany, for example, have pupils with a more mature attitude to clothes, in my experience.