Class analytics: the aggregate picture
Analytics rolls a class's data up: completion rates, common failure points, and time-on-task across everyone - the pattern-spotting view, not the moment-to-moment one.
Select the class, then open Analytics. This is where a whole class missing the same concept becomes visible - worth revisiting before the next lesson.
Analytics scopes to whichever class is selected in the Classes tab. See "The class activity feed" for the real-time counterpart to this aggregate view.