Un-associate an Assignment with a Grade Item:
Click the Assignment Tool on the course navigation menu
From the Assignment Folders list locate the Assignment item>Click the action triangle to the right of the item>Click Edit Submission Folder
From the Properties tab>click the dropdown arrow next to Grade Item>Choose None from the Grade Item dropdown>Click Save and Close.
Un-associate a Quiz with a Grade Item
Click the Quizzes tool on the course navigation menu
Click Quiz title
From the edit quiz window>Click the Assessment tab
Click the Grade Item dropdown arrow and choose none
Click Save and close.