When I'd first enrolled in the OASIS public school system, I was required to give them my real name, avatar name, mailing address, and Social Security number. That information was stored in my student profile [...]
Ready Player One by Ernest Cline, chapter "0002"
The OASIS public school system is tied to the person in the real world, through their real name and SSN.
Presumably, when an avatar dies, the student has to create a new avatar and register it with histheir account.
If my avatar was killed, I would lose my sword, shield, and leather armor, and the three levels I'd managed to gain over the past few years. I'd have to create a new first-level avatar, which would spawn at my last log-in location, in front of my school locker.
Ready Player One by Ernest Cline, chapter "0007"