What happens when a staff member leaves?

Deactivate their account and hand over their courses. What they recorded stays.

Deactivate their account

An admin deactivates the account in Team. A deactivated account can't log in.

Hand over their courses

Change the teacher on each of their courses in Course settings.

What happens to their records

The attendance and changes they recorded stay as they are. The audit log shows who changed what, and when.