I want to take the point Amanda Marcotte makes in this excellent Slate piece, and generalize.
She's discussing a middle-school teacher expressing concern about how girls shouldn't just see themselves as sex objects for men. The teacher then does a bunch of sexual policing on how short the girls' skirts are. This, as Amanda explains, is no good. Determining your worth by how good a sex object you are for men is no good, and determining your worth by how good you are at advertising that you're not a sex object for men is similarly no good.
What determines a woman's value? Well, the same thing that determines a human being's worth in general. Are you kind? Do you try to develop useful skills and work hard so that you can help others? Do you avoid telling lies, stealing things, and generally causing trouble for everyone? These are the sorts of things that make someone a good person. They're compatible with being chaste and wearing dresses that cover everything up, and they're also compatible with fucking a new guy every week or day and wearing the naughtiest clothes that don't get you thrown out of school or work.
If you're looking for the educational environment that expresses the right attitudes towards women's clothing and attitudes towards sex, it's a very diverse one where nobody cares about that stuff. In my class at NUS, I don't care whether you're a heavily covered-up Muslim or a foreign exchange student whose dress expresses your delight at being on a warm tropical island. And I don't care whether you're a virgin or if you've had sex with a hundred people. Anyone who has done the reading, has thoughtful things to say about it, and helps our discussions move forward is welcome in my class.