Breaking a Course Over Multiple Years

SAT Prep is part of what we teach in 9th, 10th, and 11th grade in our English department. We're thinking about breaking it up where each year is responsible for one unit. If a student takes "SAT Prep" and completes the first unit, and then the next year joins another "SAT Prep" with a different class/teacher, does their progress on the subject carry over? Or when they start the subject in that new class, does it start from scratch?

The way this works is kind of important to our ability to scale Kahn Academy over multiple years.