What grade do you use for students who have left. Before we converted, our student billing made a grade for former students. After conversion, we merged with records from the registrar/admissions office and they kept the grade that the student was in when they left.
We use the same grade in Student Billing, Admissions and Registrar's, I just change the billing status to non-active and the student status we change to Not-Returning, Expelled, etc.