10.5.4: AD administer group users lose rights when off network

We have 10.5.4 laptops and AD user authentication. Teachers are to be admin users by the "allow administration by" option in the Directory Utility Active Directory services. The teachers log in to the computers and their account on campus shows admin, mobile. They, however, appear to lose their admin rights when they go home or off of the schools network. Has anyone else encountered this?