Now comes some new experimentation which supports that notion. TutorText (that's 1961) has been mentioned once or twice. I had high school classes, maths if I recall correctly, using them. More than 50 years, and the notion of immediate testing has again been established.
"We found that you do better when you test yourself, rather than restudy, and that it didn't matter if you had A.D.H.D. or not," Dr. Knouse said in an interview. On average, the students recalled about 35 percent of the words they had studied twice, and 45 percent of those they studied once and then quizzed themselves on.