With Khan Academy I recall they tried exposing some measure of competencies on different aspects of a subject based on their testing, so as the interactive human / 'teacher' you could help the student more specifically and not waste time drilling on what they know, and especially not waste time on canned lectures done better elsewhere which everyone can watch as homework.

A fun if unrealistic alternative, have the professor move fast enough to give the illusion of individual clones for each student: https://youtu.be/ZJy8qH8Fw5s