Depends on the school, really. I suggest that you talk to someone in admin.
I get a lot of students who ask me to call them something quite different from their legal first name. I always do. But their ID (and eventual diploma) shows only the legal name. I don't know if my school has a provision for changing a name, or adding an alias, where there is no legal documentation. I've heard that some schools will record a preferred first name but not a complete change unless there is documentation. But the best people to ask is your school.
Obviously, there's no substitute for a legal name change. Do you want to change your name legally, and are you in a position to do so?