Create a course with a student, the course must have at least one section. Create an assignment with the 'Hide Grader' option enabled . Log in as the student and add a submission to the assignment. Log in as teacher and grade the submission. As admin, enable "Mobile services": Plugins ► Web Services ► Mobile Create a Token for the student user Click on Site administration ► Plugins ► Web services ► Manage tokens Next, you can do a CURL REST call simulating a WS client with the student user . You need to replace the wstoken, assignid (the assign instance value) and the URL of your moodle instance curl 'http://localhost/m/stable_master/webservice/rest/server.php?moodlewsrestformat=json' --data 'assignid=1&wsfunction=mod_assign_get_submission_status&wstoken=a70d553bbaf6d9b260a9e5c701b3c46e' --compressed Confirm that No exception is returned. The value of feedback->grade->grader is -1.