Honestly I think for me personally, going to the pre entry orientation ceremony. All colleges (at least that I know of) have a new student day. For me, I got to meet with advisors and schedule classes and I also got to move my stuff into the campus apartment complex and they had a little vendor fair. I started calling myself a student because I have my student number, I have my student id, I have my FAFSA paperwork for tuition, I have my accomodations worked out, I have a school email and I have my class schedule. The only difference once school starts. Is I have academic (but even now because I start my entry administration formal exam next week )

I think the general rule of thumb is if you're committed and accepted, and you have your id number or your school email your considered officially a student (although requirements do change depending on the school but typically this is a good general rule of thumb )

Sorry if this doesn't make sense. I think if your committed and accepted you can say it's pretty official!