Elementary school students' ability to comprehend and study expository material begins to be a major concern primarily in the fourth grade. Chall's (1983) characterization of this period as the "fourth grade slump" (p. 67) remains a valid observation, because teachers still report that while children continue to show ability to read narrative material during this period they are unable to completely read and understand their content area textbooks.
Walker, M. L. (1995). Help for the "Fourth-Grade Slump"—SRQ2R Plus Instruction in Text Structure or Main Idea.. Reading Horizons: A Journal of Literacy and Language Arts, 36 (1). Retrieved from https://scholarworks.wmich.edu/reading_horizons/vol36/iss1/3