Why is Glinda exempt from the Shiz dress code?

I assume Elphaba is exempt because of her (somewhat) independent study program (although she obviously takes regular classes, so...) but Glinda seems free to just wear whatever. Any textual evidence that I missed in either stage or movie?

Edit: to be clear, I'm not letting this interfere with my enjoyment; I just love asking experts these kinds of questions. You get answers like "Well during the Philadelphia run in 2004 there was a line..."