Worcester, D. A. (1928). The permanence of learning in high school subjects—algebra. Journal of Educational Psychology, 19(5), 343-345.
http://dx.doi.org/10.1037/h0073822
Three forms of the Douglas Algebra Test were given in February, March and May respectively and again in December. The first two forms contains material which was learned early in the school year. Of this material little had been forgotten. On the other hand, Form 3 contained material learned late in the year. In this case the amount of forgetting was immensely more than in the first case. The study of forgetting in school subjects will be continued. (PsycINFO Database Record (c) 2016 APA, all rights reserved)