https://help.blackboard.com/Learn/Instructor/Original/Grade/Navigate_Grading


About Deleting Grade Center Columns

When you create gradable items in your course, grade columns are created automatically in the Grade Center, including columns for:

  • Tests, surveys, and Self and Peer Assessments
  • Assignments and SafeAssignments
  • Discussion posts
  • Journal and blog entries
  • Wiki contributions

The only way to delete these auto-created grade columns is to first delete the gradable items in your course. For some, if no student submissions exist when you delete the item, the Grade Center column is deleted automatically or you are allowed to decide whether to delete the column. However, when you delete a SafeAssignment in your course, you must also delete the corresponding column in the Grade Center.

WARNING! 

Before deleting gradable content in your course, you must carefully consider what the ramifications may be. Student work, such as test and assignment submissions, is deleted along with the deletion of the content item in your course. The action is final. In some cases, you can choose to save the grades assigned in the Grade Center. Even if you retain grade columns in the Grade Center, you cannot access the student submissions because they were deleted with the item in your course. Alternatively, make the gradable item unavailable in your course to preserve the submissions and the scores in the Grade Center.

You are not allowed to delete the default user columns and the external grade column. If you set a grade or calculated column as the external grade column, you must select another column as the external grade column before you can delete the first one.