Anyone who’s ever scratched their head over their car manual or struggled to parse a website’s terms of service knows: It’s hard to read about a topic you don’t really understand.
It’s a common-sense statement that’s backed by research. Studies have shown that readers use their background knowledge—vocabulary, facts, and conceptual understanding—to comprehend the text they read.
Much of this evidence isn’t new. But it’s received more attention now, amid the “science of reading” movement.
In recent years, a growing number of parents, teachers, and reading researchers have called for changes to early literacy instruction, to bring it more in line with the evidence base around how children learn to read. Often, schools weren’t taking research-based approaches to teaching students a crucial building block of reading—how to sound out words. If kids can’t get the words off the page, they can’t extract meaning from text.
Over the past three years, about two dozen states have passed laws mandating that students are taught these skills in an explicit, systematic way.
Over the past few years, more states have passed laws or implemented new policies related to evidence-based reading instruction. Look below to see which states have such legislation and when it passed.
Click here to learn more about each state’s legislation or policy.
At the same time, though, some science of reading advocates have said that foundational skills instruction isn’t the only piece of literacy learning that needs an overhaul. They argue that schools also don’t do enough to support students’ background knowledge—a key factor in their understanding of any text. That’s the issue explored in The Knowledge Gap, a book that’s made its way onto district leaders’ reading lists and into teacher professional learning groups.
Over the past few decades, reading comprehension instruction has become “content agnostic,” focused on skill practice, to the detriment of learning about science, history, and other disciplines, said Sonia Cabell, an associate professor at Florida State University’s College of Education.
“In the No Child Left Behind era, and the Reading First era, reading became the main focus. Reading blocks were lengthened. This pushed out the science and social studies instruction,” Cabell said, referring to the 2002 federal law and a $1 billion-a-year reading program it created.
Cabell and other researchers who study the integration of content knowledge and literacy instruction say the focus on “knowledge building” holds promise. But they also say there are a lot of unanswered questions about how these approaches should be designed, and how much they can actually improve reading achievement.
Here’s what experts and research say about what a greater focus on content knowledge could mean for reading instruction.
What role does background knowledge play in reading comprehension?
A big one. Decades of studies have shown that children can understand text better if they have some background knowledge about the topic. (See here for a recent review of the research.)
This may seem like an obvious finding: Of course, kids can understand a book or an article better if they already know a bit of what it’s about. It’s likely easier to read a text about paleontologists, for example, if you already know the words “fossil” and “extinction,” and you know that animal species that used to exist have since died out.
This applies even for children who are otherwise poor readers. One example of this is what’s often referred to as “the baseball study.”
In a 1988 paper, researchers Donna Recht and Lauren Leslie divided middle schoolers up into groups, based on two factors: their general reading ability, and their knowledge about baseball. Then they asked the kids to read a passage about a game.
They found that the baseball lovers who scored low on a general reading test could understand and recall the text better than the higher-scoring kids who didn’t know as much about the game.
So, background knowledge about a specific topic is helpful in understanding text on that topic. But what about in general? Does knowing more about the world lead to better reading comprehension overall?
A large body of research shows a correlation: Children who score higher on tests of general knowledge are better readers. These kids also tend to grow more than their peers in reading comprehension over time, said Gina Cervetti, an associate professor at the University of Michigan’s School of Education, who studies the connections between literacy and content-area learning.
But other factors could play a role, too.
“Those kinds of correlations are tricky, because there are a lot of other things that are going on,” said Timothy Shanahan, an emeritus professor of education at the University of Illinois Chicago. People who score higher on tests of general knowledge also tend to have greater language ability, and tend to be from higher-income backgrounds.
If background knowledge is linked to reading ability, does teaching knowledge help kids become better readers?
It can. But there are some caveats.
There are a few different ways that teachers can connect content knowledge and literacy instruction in the elementary school day. One option is to merge the two—to embed literacy instruction into social studies and science, teaching students cognitive strategies to help them engage with the content.
This has positive results. In a 2022 metanalysis, researchers HyeJin Hwang, Sonia Cabell, and Rachel Joyner examined studies that took this integrated approach to literacy and content-area instruction. Kids who were taught this way retained more vocabulary and understood content better than children who learned science or social studies separately from reading instruction.
These students also did better on standardized tests of reading comprehension. The integrated approach not only made them better readers of the content they were learning, it made them better readers overall.
These programs weren’t teaching kids ... knowledge as a set of facts to be learned. These kids were learning deeply about a set of concepts.”
Another approach is to build it into reading classes, developing English/language arts units that are structured to deepen students’ understanding about different topics. This is often the approach advocates are referencing when they promote high-quality or “content-rich” curriculum.
This method has shown more mixed results.
Most studies of this approach find that it has a positive effect on students’ knowledge of the subject in question—for example, teaching a 4th grader about the American Revolution will likely mean that they know more about the American Revolution. But only some of these approaches lead to higher scores on tests of general reading comprehension.
One that does is the Model of Reading Engagement, or MORE. It was developed by Harvard education professor James Kim and his colleagues.
The approach aims to build students’ science content knowledge through literacy lessons. But it’s not just focused on acquiring facts. The researchers designed the lessons with the goal of helping kids to build a schema—a mental model that they could then apply to understand new, related concepts.
The overarching theme of the program, in this case, was how scientists study past events. Throughout 1st and 2nd grade, students learned about interrelated concepts that would build that schema. Units centered on how animals survive in their habitats, and how paleontologists study prehistoric animals and events. A 2023 study from Kim and his colleagues found that the approach helped students apply the science vocabulary and concepts they learned to other contexts.
Kim’s study, and others that have shown general effects on reading comprehension, hold something in common, said Cervetti.
“These programs weren’t teaching kids a bunch of knowledge at a superficial level. It wasn’t knowledge as a set of facts to be learned,” she said. “These kids were learning deeply about a set of concepts.”
Still, in Kim’s study, there was a limit to how far kids could transfer the knowledge that they learned. Generally, the new texts had to include explicit connections to the words and concepts they’d learned. If the familiar concepts were missing, students couldn’t make the connections themselves.
If kids can’t make connections between related topics, “it’s a signal to teachers of what they need to go back and discuss,” Kim said.
How should schools decide what kids should read and write about? What knowledge should be the focus?
This question has dogged the American education system for decades—if not centuries.
It’s the debate at the heart of many decisions about teaching and learning. The conversation is particularly volatile now, as parents’ groups and Republican legislators seek to limit what students can read and discuss in the classroom.
Studies’ insight on this topic is limited. Evidence would suggest that students’ curiosity should play a role, Cervetti said. There’s a large body of work demonstrating that student interest and motivation have a strong impact on academic achievement.
But outside of that, things are more fuzzy. What’s the right balance of depth versus breadth in topics? What knowledge will best prepare students for their lives outside of school? Researchers don’t know.
Still, some education scholars have offered prescriptions. Perhaps the most well-known—and certainly one of the most debated—of these roadmaps was developed by E. D. Hirsch Jr., a professor emeritus of education and humanities at the University of Virginia and the modern father of the knowledge-building movement.
Hirsch popularized the idea that students needed to learn about something in order to read well. In his 1987 book Cultural Literacy: What Every American Needs to Know, Hirsch outlined a list of essential figures, events, and concepts. He tried to identify the background knowledge that would comprise a sort of cultural canon—the information that most writers and speakers would assume their audience shared.
Its contents provided the framework for Core Knowledge Language Arts, an ELA curriculum. But Hirsch’s work also saw a swift and strong backlash from critics who said his list was Eurocentric and elitist.
Hirsch has argued that the approach he advocates is a way of providing equal opportunity, putting children on an even playing field with a shared reserve of knowledge—regardless of their cultural, racial, or socioeconomic backgrounds.
Still, the question of whose knowledge matters—what’s important for children to know and who gets to decide—is far from settled.
Some more recent efforts have used Hirsch as inspiration. The Johns Hopkins Institute for Education Policy has created Knowledge Maps, tools it uses in work with districts looking to evaluate how and where their curricula build knowledge.
The Knowledge Maps are based on Hirsch’s core knowledge guidelines with some additions and changes—such as added criteria around diversity, equity, and inclusion, said Ashley Berner, the director of the institute.
Other programs have taken different approaches. In the MORE intervention, Kim and his co-authors tried to choose content that was “timely and timeless.” Timely, in that it aligned to current state standards in science. And timeless: It has shown up consistently in state standards over the past two decades, and science professors think that it’s relevant and accurate.
Of course, these are still subjective decisions—an inevitability in choosing knowledge, said Shanahan. “When it comes to certain aspects of the arts, and science, and social studies, what content do we want kids to know? Those are value judgments,” he said.
Is knowledge the only factor in reading comprehension ability?
Far from it. Children don’t just need to learn information. They also need to know how to organize it in their minds, use it, and apply it in new contexts.
Teaching comprehension strategies can help students become skilled at these tasks. Decades of research have shown that explicitly teaching students how to use these strategies—like summarizing, visualizing, creating graphic organizers, and asking questions about their understanding—makes them better readers.
Teaching students about how different types of text are structured has also been shown to improve reading comprehension.
“This is a clear case in our field of a ‘both-and,’ not an ‘either or,’ said Nell Duke, the executive director of the Center for Early Literacy Success at Stand for Children.
In fact, most of the knowledge-building interventions that show positive effects in the research literature have combined content-area instruction with these kinds of strategies for metacognition, said Cervetti.
Cervetti thinks it’s likely that deep content area knowledge and students’ ability to use comprehension strategies reinforce each other.
“Imagine being a kid who has read lots of texts, but every text you encounter is unfamiliar ideas and unfamiliar words,” she said. “You get through the text and you walk away having understood something about that text. But probably not enough to be a better comprehender.”
With these topically disconnected texts, the student doesn’t have the chance to practice the strategies that good readers use, Cervetti said, like making connections or asking questions prompted by prior knowledge. But if the texts work together to build a bigger conceptual understanding, they do present those opportunities. Knowledge, she hypothesized, “builds momentum” for kids to practice the comprehension strategies that research shows are powerful tools.
There’s also some evidence that knowledge-rich contexts naturally facilitate richer conversations. A 2013 study by Cabell and her colleagues found that preschool teachers used more sophisticated language structures when they integrated reading and science instruction.
What do all of these findings mean for classroom practice?
The main takeaway is that reading instruction should be engaging students in deep, substantive ideas, said Cervetti.
Yes, learning about something—having clearly defined topics—is important. But these topics need to help students build a broader, conceptual understanding.
That means that instead of learning about “oceans”—an umbrella that could encompass everything from reading news articles about microplastics to studying Moby Dick—a unit might be centered around a theme, such as, “we have one connected water system.”
Some English/language arts curricula attempt to structure units this way, developing them around social studies and science ideas. But Duke cautioned that these ELA programs shouldn’t be seen as a substitute for instruction in other subject areas.
Science and social studies don’t just teach content; they also teach discipline-specific practices—like developing a hypothesis or analyzing a primary source. “That kind of information, in my perception, doesn’t tend to make it into ELA curricula,” she said.
“I think an increasing segment of the field is picking up on the idea that content-rich English/language arts instruction is better for kids,” Duke added. “But it has not fully tackled the question of, when in our day is there space left for science and social studies? And [there’s] little attention to, how do we coordinate that across the school day?”