I would guess that the student you are trying to remove is not found in the list so it is not reomving anything.
The reasons for this could be:
1) It isn't there
2) The equals method for the student in the list and the one you are passing in do not match.
Are you creating the student manually or retrieving it from the list prior to removing it?
If that's not the case then I think you need to provide a little more information then we can give you a bit more help
Regards
