No wishful thinking can change what we are born
The notion that people can "choose" their gender is ridiculous. Why not allow people to choose their species too?
The reality is, with regard to our species and gender, we are all born what we are born, period, and no amount of wishful thinking will ever change that.
Therefore, given the reality of genetics, any rule that would permit persons to "choose their gender identity" would actually be aiding and abetting a person in a delusion.
Students with "gender identity" issues should be provided mental health counseling aimed at helping them to accept themselves for who they are. They should not have their delusions perpetuated by the state.