Thanks Al. I do know it's supposed to behave that way (and I appreciate that behavior for almost all other instances!) That was offered as one of the suggestions for removing the grades that come back with a student that had previously taken a course (his grades still show up, even after resetting and removing grades).
So, I'm still stuck with this problem: we have a student that took a course last year and did poorly. This semester, he's re-taking the same course. Instructor reset the course, un-enrolling all students, deleting all grades. Yet, when we enrolled the student, ALL of the grades from his previous semester showed up again. We're updating them as we go, but we'd prefer to wipe them out (when he uploads an assignment he sees a message saying he's already done this assignment, etc.).
Thanks to all for any ideas/suggestions,
Lisa