Highlighting isn’t intuitive. Students commonly have difficulty spotting key ideas, opting instead to indiscriminately mark up the text or selectively highlighting intriguing but extraneous details. As novice learners, they tend not to think about the larger organizational structure of a text, or the importance of distinguishing main ideas from supporting details.

To students, of course, what they’re doing seems productive. The act of tracking each digested line of text with bright strokes of the highlighting pen can feel intellectually satisfying—like making real progress.

But for students to highlight productively, teachers need to step in. Spending as little as a couple of hours tutoring them on proper highlighting techniques—how to take a spartan approach and distinguish main ideas from supporting ideas, for example—can yield a 325% improvement in effectiveness, according to a 2022 meta-analysis. More importantly, the researchers say, highlighting should always be paired with other learning activities that promote further critical engagement with the text, such as having students write practice questions to test their knowledge of material or use graphic organizers to re-evaluate their thinking about key concepts.