A graduate teaching assistant is now "staff?"
As I recall, a little over 10 years ago when we had the NLRB talking about players being employees, one of their rulings was any grad student at a private school is considered an employee/or staff member.
However, they did point out in those rulings that their status would change per state law/state university.
I'm far from an attorney and I don't know a lot of about GA state law but I'd imagine it would be pretty hard to argue against a person being a staff member when they are teaching and getting a paycheck from that school.