This is how I understand your question:
Q1: Why do we need the
??? category at all? Why not have:
Keep in mind that
job is a very generic word in English, it does not merely mean "a paid position of regular employment" (Google), it also means:
Dictionary.com: anything a person is expected or obliged to do; duty; responsibility:
Merriam-Webster: a specific duty, role, or function
Macmillan: your duty in a particular situation or organization
So the question "what is your job" can be legitimately answered with "I am a student".
However, in your specific context, I have no idea what you're trying to distinguish "student" from.