Time is the Variable

Learners advance (progression) to the next Performance Level in a content area once proficiency or better has been achieved and validated. There are no traditional grade levels.
Progression can occur at any point during the course of the year for any content area.
At the beginning of the traditional school year, learners resume their learning at the point where they left off the previous year (continuous flow). There is no social promotion.
Learners are typically in different Performance Levels for different content areas.
Multiage classrooms are the norm not the exception.