Problems with Managed Printers

Our school has two main types of users: Faculty and Students. We want Students to be able to print to one list of printers and Faculty to print to a different list. In Workgroup Manager I have specified the lists and when a user logs in they can see that list and print with no issues. The problem is that after they log out of a public computer, their list is not cleared away. So if a Faculty user logs in after a Student user (or vice-versa), they can now see both lists of printers combined. Is there something I am missing to make this work?

Thanks for your help.