We forget 80% or so within 24 hours (it's called the Ebbinghaus Curve of Forgetting) unless we review the material using the Review Cycle.
The Review Cycle says we should revisit what's been learned after 10 minutes, 24 hours, a week, a month and then six months.
So, next time you are setting your class spelling or vocabulary tests try doing it like this and see what happens:
- Set them about three words to learn
- Next week set them those three but also three more
- The following week set them those six plus three more
- Ad infinitum
And remember, using the review cycle has been shown to improve memory by 400%