This is not intended to be an academic discussion, and I’m not the right person to be citing tons of research and scholarly thought. But my undergraduate psychology major, and my experience as a teacher makes this statement seem very true: students forget; and reviewing material previously covered is essential to the student’s retention of that material.
Well, it turns out that research backs this up. Psychologists compared retention between 2 groups: one group studied in one mass session. The other group studied the same amount of time, but the time was distributed over several sessions. The retention of the 2nd group was significantly greater than the 1st group. Re-exposure to the material to be learned reinforced the learning, and led to greater retention.
Krug, D.; Davis, T.B.; Glover, J.A. (1990). Massed versus distributed repeated reading: A case of forgetting helping recall? Journal of Educational Psychology, 82, 366–71
Some homeschool educators, and many students, aren’t fond of quizzes, tests and exams. But testing is an important part of the learning process. Studying for a test reinforces the student’s learning of the concepts, and will improve their retention. Material re-studied several times, first for a quiz, next for a test, and finally for an exam, has been carved much deeper into the brain’s neural networks.
Adding regular Quizzes, Tests and Exams to your student’s curriculum creates natural review periods, and increases retention of the material that’s been studied.