The student role and grad year will need to be removed for the manager to be able to view the report cards without conflict. To do this:
  1. Navigate to Core > Users
  2. Under the Edit User Profile Data tab search for the user
  3. In the System Information section click Student Enrollment
  4. Click Edit next to each enrollment row
  5. Click Delete and Confirm for each enrollment row.

This will remove any record of the user being enrolled. Once that is removed the student role will no longer be assigned and there will be no conflict generating report cards.