Setup an assignment that doesn't require any file submission or feedback and uses simple direct grading. When the teacher goes to View/grade all submissions, in the Options section, set Assignments per page to all and put a check mark in the Quick Grading box. You can even use a custom scoring or the regular 100 point scale. After using the drop down to mark a grade for one or more students, the teacher will need to remember to click on the Save All Quick Grading Changes button. My sample in the photo only shows one student, but it will work for many and also for groups.
Hope this helps,