Not many (including me) are fans of Login as feature when it comes to a teacher uploading assignment on behalf of the student. Although there is a capability to activate this for teachers it is ticked off by default. This is because organizations don't want to give access to a student's account for reasons like a. teacher will be able to see all grades of the student from different modules even where the user is not a teacher b. etc.
In reply to Shu Doi
Re: Can a professor upload assignment on behalf of student
by Christine Healey -
As admin, I can use this feature. It's helpful when sorting out problems the student may be experiencing in using Moodle - I can talk them through what they are seeing in a phone call, for instance.
However, I have come across a situation where a teacher with 'login as' was tweaking the student's work and uploading it to assignments - cheating, in other words.