Require login for assignments?

Right now, I am creating assignments in Khan Academy and also sharing a link to that assignment to Google Classroom. I repeatedly tell students to make sure they are logged in to Khan Academy so that I can see their score and then enter it in Google Classroom, but some students forget (and some "forget") to log in, and, as a result, I have no score for them.

Is there a way to require students to log in before completing their assignments? My Google Classroom rosters are synced with Khan Academy, but that doesn't seem to ensure they are logged in when they access the assignment through a Google Classroom link.