I propose "self-contained-ness" or "comprehensiveness" of class/course.
The following picture shows :
Left
: "Moving up to higher grade" and "piling courses", from red to blue.
Right
: Each course is "self-contained" -- from red to blue.
The right is an image of the ideal parallelism between "moving up to higher grade" and "piling self-contained courses", to which the left should be changed.
