Do your students have trouble maintaining skills from previous lessons, units, or grade levels? "I taught it, they just don't remember it."  How often have you said or heard this statement? "Retrieval practice boosts learning by pulling information out of students’ heads, rather than cramming information into students’ heads."  Many retrieval practice techniques do not require additional planning and have the potential to improve students' ability to retain information over time. 

Source: https://www.retrievalpractice.org/why-it-works