It's not a proof so much as a disproof of the idea that transgender individuals are not the gender they "identify as". In other words, it establishes gender identity as a legitimate concept. For example, individuals with complete androgen insensitivity syndrome (CAIS) are typically born phenotypically female, have a female gender identity, and are attracted to males -- but they have a Y chromosome and internal testes. Are they men or women? Well, the easiest answer is to actually go by the person's reported gender identity. The rarity of the occurrence is irrelevant.
For some reason, I always find it amusing when other people try to tell transgender or intersex people what they are, gender-wise. The world is more complicated than a middle-school biology textbook, and people who feel the need to police transgender people's gender identity/expression seem to forget that they are a drop in an ocean of seven billion people.
Why not take Jessica to another school where nobody knows her so she can spend the rest of her life actually being seen as Jessica instead of Johnny in a dress? Is common sense really that hard for you?
