"Subject = Greek,
Possible Classes = Greek 101 for first year students, Greek 201 for second year ..."
No, Carl, I think Nagita is right, and that you will run into trouble at latest in the new term if you mix classes and class instances. The name "subject" should not mislead us to ignore that we have only 2 hierarchy levels, i. e., "department" (that does not deserve this name), and class.
Therefore I would recommend to use "Greek" as the higher hierarchy level ("department"), and "Greek 101 for first year students" or "Greek 201 for second year" as the lower hierarchy level (class). Otherwise, mapping Fall and Spring instances will be almost impossible.
Another problem is that the system abuses these NAMES as ADDRESSES in URLs such that these URLs violate a central Web-Design rule #9 of http://www.useit.com/alertbox/20021223.html .
