Spaced repetition schedules each question’s next review using an algorithm. The School add-on offers two: SM-2, the default since spaced repetition launched, and FSRS, a modern alternative. The scheduler is chosen once for the whole site, and everything else about spaced repetition works identically with either choice.
Choosing a Scheduler
- Navigate to PressPrimer Quiz > Settings > Spaced Repetition.
- In the Scheduling Algorithm section, choose SM-2 (classic) or FSRS.
- Save the scheduling settings.
The Two Algorithms
SM-2 (classic)
The classic SuperMemo-2 algorithm. It is simple, well understood, and has been the default since spaced repetition launched. Each correct answer stretches the interval to the next review; each miss shortens it.
FSRS
FSRS (Free Spaced Repetition Scheduler) is a modern, open source algorithm used by popular flashcard tools. It models each student’s memory of each question with two values, stability and difficulty, and schedules the next review to hit a target probability of recall. In practice this usually means fewer, better-timed reviews for the same level of retention.
With FSRS selected, a Desired retention setting appears. This is the target probability that a student still recalls a question at the moment it comes up for review. The default is 90%, and it can be set between 70% and 97%. A higher target means more frequent reviews; a lower target means fewer reviews with more forgetting between them.
Maximum Interval
The Maximum interval (days) setting caps how far out a review can be scheduled, regardless of algorithm. The default is 365 days. Well-known questions will never be scheduled further out than this, which keeps even mastered material coming back at least occasionally.
What Happens When You Switch
Switching schedulers is safe and gradual. Existing review schedules are not recalculated in bulk. Instead, each question converts to the new algorithm automatically the next time that student reviews it, and its future scheduling follows the new algorithm from then on. You can switch back at any time and questions convert back the same way.
Nothing visible changes for students except the timing of reviews. The review dashboard, mastery statuses (Learning, Reviewing, and Mastered), reminder emails, instructor reports, and xAPI statements all behave identically under both algorithms.
Which Should You Use?
If your spaced repetition program is working well, there is no need to change anything; SM-2 remains the default and is fully supported. FSRS is worth considering for long-running programs with a lot of review volume, where its more precise scheduling can reduce the number of reviews students need to maintain the same retention.
For an overview of spaced repetition itself, including enabling it on quizzes and the student review dashboard, see Spaced Repetition.