Moodle Forums can be graded through whole forum grading or a process called rating

Whole forum grading is a new Moodle feature that allows instructors to assess student forum postings from a grading interface that collects all student postings and displays them on one page. 

Ratings are selected for a post from a scale that can be customized. When ratings are enabled for a forum, a grade item is created in the gradebook. Ratings are sent directly to the gradebook. Selecting the Aggregate type will determine how the gradebook calculates the ratings.

When rating is enabled, the instructor will see a drop-down menu on each entry (not their own), allowing them to select a number from a scale to rate the post. Users can rate more than one post at a time. 

Set Up Whole Forum Grading:
  1. On your desired course, click on the forum that you want to grade.
  2. Click on the GEAR (gear icon) located at the top right, then click on Edit settings.
  3. On the forum settings page, scroll down and click the  Whole forum grading.
  4. Adjust the grade settings to your preference.  -- NOTE:  the default is 100 points.  You must edit this if you do not want100 points assigned to the forum.
    Whole forum grading settings 
  5. Once finished, click Save and return to course or Save and display to save your settings.
    "Save and return to course" and "Save and display" buttons 
  6. Once saved, go back to your desired forum and click on Grade users.
    Grade users button 
  7. The whole forum grading interface will appear. It contains all of a student's forum posts on left side of the screen while their name, a grade entry field, and communication option will appear on the right side of the screen. Their forum posts will contain post titles, dates and their content. You can scroll through all the students by clicking the arrow, or search by name by clicking on the magnifying glass.
    Whole grading forum arrow and magnifying glass button to choose student to grade 
  8. Click Save located on the top right side of the page to save grades after you have finished inputting all grades.

    Save button for whole forum grading