If you want to set a default grade for a certain assignment, use the assignment drop-down menu. This will allow you to input scores for students who do not have scores or to overwrite already entered scores.
Click the Marks link.
Hover over the assignment title and click the drop-down menu.
Click the Set Default Grade link.
Type the default grade in the text box [1]. If you would like to overwrite existing grades for the assignment, select the Overwrite already-entered grades checkbox [2]. Click the Set Default Grade button [3].
Click the OK button to view the new default grades.
Default grades are automatically entered for all students who do not have a grade. Grades can be changed by clicking the default grade and typing in an updated score.