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The Power of Prior Knowledge

Gene Kerns finds that this year’s What Kids Are Reading report supports the idea that familiarity with a topic can help even struggling readers read more

According to the most recent National Assessment of Educational Progress (NAEP,, approximately a third of students across grade levels demonstrated reading proficiency. The precise figures were 35% in fourth grade, 34% in eighth grade, and 37% in twelfth grade, reflecting a decrease in the fourth and eighth grades since 2017, following decades of flatlining. These figures make it tempting to slide into doom and gloom about literacy and education in America.

And yet, in the most recent edition of the What Kids Are Reading report (, which gathered data on 271 million books read by 7.6 million students, there is reason for hope and, perhaps, even celebration.

Focusing on Nonfiction

If literacy education is on track in a school, that building has an opportunity for everything else to go well. Success in literacy spills over into success in science, social studies, math, and anything else students are learning. It’s the key to everything schools do.

To gain insights into this keystone academic skill, What Kids Are Reading, the largest annual survey of student reading habits, dives into data collected from the millions of students using myON and Accelerated Reader, with the ultimate goal of supporting teachers as they, in turn, support students in doing more reading.

With a data set this large and comprehensive, our challenge is not data but what questions we should ask of it. This year, we decided to focus on the reading of nonfiction because, over the last few years, there has been a growing interest in the role of prior knowledge in reading comprehension. It has become increasingly clear through multiple studies ( that the amount of prior knowledge students have on a topic is a powerful predictor of how well they can read texts on that topic.

Struggling readers are perfectly capable of reading advanced texts on a topic they already know a great deal about. Simply put, there’s more to comprehension than general reading skills.

Access Is Essential

As we dove into the data on nonfiction reading, the most striking finding was the huge difference in student reading practice when nonfiction texts were more easily available to them.

As mentioned, What Kids Are Reading’s data comes from myON and Accelerated Reader. With the latter, students sometimes can be limited by what they can physically get their hands on, so the scope of their reading is profoundly impacted by what books are in their school library or classroom. Classrooms, and even many school libraries to some extent, tend to be heavy on fiction. On the other hand, the collections in myON include a ton of nonfiction.

Among the students we tracked through Accelerated Reader, about 25% of their reading time was spent on nonfiction. The students using myON, on the other hand, read nonfiction nearly twice as often—students spent nearly half their reading time on nonfiction texts when they were as readily available as fiction. Our data can’t speak to a causative relationship between access and reading habits, but the correlation is undeniable.

Why Knowledge Matters

A series of studies going back to the 1980s have pitted knowledge against reading skills to determine which matters most. A classic study in this vein was published in 1988. “Effect of Prior Knowledge on Good and Poor Readers’ Memory of Text“ (, more commonly referred to as “the baseball study,” divided students into four groups based on high or low knowledge of baseball and high or low reading ability. The researchers then gave the kids a challenging text about baseball, followed by an assessment of their comprehension.

They found that the children with a great deal of prior knowledge about baseball substantially outperformed those with low knowledge, regardless of reading ability.

Another example, from 2014, is “Building Background Knowledge“ ( In this study, researchers again divided students into top-performing readers and lower-performing readers. They had the students read a text about birds, then assessed their comprehension of what they had read. There was a sizeable gap in performance between the two groups.

Next, they gave the students a passage on “wugs,” a fictional animal they had made up to ensure that no one could have any prior knowledge. When students took assessments of their comprehension of this passage, the performance gaps virtually disappeared. In other words, according to the researchers, “the gap in comprehension wasn’t a gap in skills. It was a gap in knowledge.”

Prior knowledge is a powerful aid to comprehension for adults as well. I often tell teachers that I could give them an article from an education journal that’s very complex and they’d perform very well on a comprehension assessment. If I went to the law library and found a text with the same complexity and the same readability, they may not make it past the first paragraph.

As E. D. Hirsch says, there is a theoretical difficulty of texts, and there is an actual difficulty of those same texts. The theoretical difficulty is what we can measure with readability formulas. We can measure the vocabulary, the length of sentences—all the various factors used in the variety of formulas out there. But we can’t know the actual difficulty until we place a text in the hands of a reader. If they bring tremendous knowledge of the subject, that can compensate for the fact that they might be a struggling reader.

The Value of Dwelling on a Topic

To see if we could find evidence of this phenomenon in the What Kids Are Reading data, we did two new things: one having to do with the questions we asked, and the other as a means of helping teachers put the report’s data to use for their students.

First, we looked for patterns where a student may have dwelt on a topic. We defined “dwelling on a topic” as reading three or more books on a topic or closely related topics. Analysis revealed that when students read fewer than three books on a topic, their comprehension rate was, on average, 79%. When they read three or more books, it was 83%.

The psychometricians and statisticians would have to drill down there to come to solid conclusions, but given the size of our data set and the number of kids, I would suggest that a four-point spread in comprehension is statistically significant.

The second change we made in this year’s report was identifying some topics and offering teachers suggestions for beginning, intermediate, and advanced texts on those topics. If a high school teacher is working with her students on the world wars, for example, there’s a page in the report where they can find less challenging texts on the topic for students who have little prior knowledge. They could then offer students with some prior knowledge an intermediate book on the topic, and so on. The hope is that by sequencing the books, we can help students eventually read complex texts on a particular subject.

Putting the Data to Work in Classrooms

Beyond this “stair-step” approach of sequencing students through books to develop prior knowledge, the data from this year’s What Kids Are Reading report brings up some other tactics teachers might take.

First, it suggests that educators should keep in mind the limitations of readability formulas. ATOS from Renaissance, Lexile from MetaMetrics, Fountas & Pinnell, and Flesch–Kincaid all offer pretty good measures of theoretical readability, but they do not tell us much about the actual readability of a text for any particular student. Without testing prior knowledge, they only tell half the story.

With that in mind, the recommendation we make is to manage student reading, but not too rigidly. If a student is eager to read a particular book, but their teacher knows that student’s reading proficiency is below the theoretical readability of that particular book, it’s still okay for that student to try reading that book.

I like to tell teachers that any time a student says they want to read a particular book, they should hear everything after “I want to read” the same way that Charlie Brown heard his teacher talking: “I want to read… wah wah wah.”

If a kid brings a book to a teacher that they’re interested in for some reason, rather than telling them no, the teacher might instead say, “Go ahead and try that. If you get a day or two into the book and you find it’s not what you thought, or it’s just not working out for you, come back and get another book.“

As adults, I think we all have books on our shelves that we started and then decided weren’t for us. That’s okay.

That student, however, may bring tremendous prior knowledge of the book’s content with them. Even as a struggling reader, if they know more about the topic than anyone else in the school, that book may be easier for them to read than it is for anyone else.

Taking prior knowledge into account can change how kids think about their reading abilities in a powerful way, particularly if they’re struggling. When educators and students understand that the most powerful predictor of how well students are going to read is what they already know about the subject, it gives everyone some freedom. It gives students the freedom to say, “You know what? If I pick up a book on something I don’t know anything at all about, it’s going to be challenging. I may have to start with some simpler stuff, and then gradually build my way up. If I pick up a book on something I already know about, it had better be a challenging one, because I’ve read a lot about that.”

Putting the Data to Work

Speaking more generally, this data on the importance of prior knowledge suggests, perhaps counterintuitively, that focusing on reading skills is not the most effective path to improving literacy scores.

In response to lackluster reading performance on many high-stakes tests, under No Child Left Behind many schools cut arts, music, social studies, and even science to make room for more reading and math instruction. Often this instruction was focused on the discrete skills of reading. This overskillification of reading, as I refer to it, is often unintentionally driven by state policy.

State standards may list out 150–200 reading skills students need to learn, such as determining cause and effect, understanding figurative language, and comparing two different versions of a story. Teaching students specific reading skills and strategies does make a difference, but after several lessons there is no additional benefit.

But the growing body of research on the importance of knowledge suggests that all of this may be cutting off our nose to spite our face. Every content area out there contributes to prior knowledge. What students often need to understand advanced texts is not more drilling on the discrete skills of reading, but to know the names and dates and places and references they learn about in history and art and science classes. If a text mentions a “Herculean task,” it doesn’t matter how well the student reads if they don’t know enough about mythology to know who Hercules was. If it says, “that was her Waterloo moment,” the student likely won’t understand it without having learned about Napoleon in history. To understand “tilting at windmills,” they likely need to have learned a bit about Don Quixote in a literature class.

People are trying to reframe this with questions such as, “What do our curriculum documents look like? Do they give the building of knowledge the role that it deserves? Do we have a sequence to the courses and classes and knowledge that builds over the years?” A subject like science is always going to be knowledge-laden, but it’s becoming increasingly clear that we have to focus on the knowledge students need to succeed in language arts as well.

When we choose a book or a text, we are choosing the knowledge we’re going to teach. For example, if a sophomore English teacher decides that To Kill a Mockingbird is one of the books her kids are going to read this year, that’s a knowledge choice. She has decided that, of all the possible novels her class could read, this is the one that may give them the most social-cultural capital.

That’s a fine decision, but educators around the country are weighing that. If students are going to spend 13 years in school, what literature should teachers collectively expose them to? What knowledge do our students need to go out into the world? The data from What Kids Are Reading and elsewhere is telling us that more conversations about knowledge, coupled with less emphasis on the discrete skills of reading, may be a more effective path to improving literacy.


Hirsch, E. D. (2019). Why Knowledge Matters: Rescuing Our Children from Failed Educational Theories. Harvard Education Press.

Dr. Gene Kerns (@GeneKerns) is the chief academic officer at Renaissance. He is a third-generation educator and has served as a public school teacher, adjunct faculty member, professional development trainer, district supervisor of academic services, and academic advisor at one of the nation’s top edtech companies. He has trained and consulted internationally and is the coauthor of three books.

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