Answer:
Sal Khan focuses on student's mastery on subject/topic.
He compares learning to the building of a house which a building contractor commences. Having laid the foundation and made about 75% progress on the foundation laying, he proceeds to laying the floors. He lays the 1st, 2nd floors on a wet foundation and moves to lay the 3rd floor but at this time everything collapses.
The process truly matters.
A student who haven't mastered a text/topic and goes ahead to another class or topic may encounter a problem in the upper level. If a student scores 80% in a class, it shows that there is a 20% which he is yet to grasp and master.
It's very important students comprehend and master topics/texts before heading to the next stage. What is fixed is that they actually master the subject/topic/text.
