A (Relatively) Easy Way to Boost Reading Comprehension

Teaching students to understand complex sentence structure can be powerful, a recent study suggests.

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For decades, reading comprehension instruction focused primarily on having students practice skills and strategies—like “making inferences”—in isolation from any particular content, contrary to what the research indicates will work. That’s still happening in many schools, but an increasing number are shifting to an approach that puts building content knowledge in the foreground and brings in comprehension strategies as appropriate to the content.

That represents progress. But reading comprehension is really complicated, and there’s at least one more major component that has gotten short shrift: familiarity with complex syntax, or sentence structure.

One reason syntax has gotten so little attention may be that the problem often doesn’t become apparent until students reach higher grade levels, after reading instruction is assumed to be over. The syntax of written language is more complex than the syntax of oral language; it’s been found that even children’s literature uses more complex sentence structure than everyday conversation. Still, in the early grades, texts have relatively simple sentence structures compared to those kids encounter in middle or high school. A child may be a competent reader in second grade but then become a struggling one in sixth. Complex syntax is likely a significant factor.

Another possible reason for the lack of attention to syntax are the silos within the scientific community. Much of the research on students’ struggles with syntax comes from speech and language pathologists rather than reading experts. Syntax comprehension problems clearly do affect reading ability, but they’re often categorized as a “language impairment” rather than a reading disorder. If children are diagnosed as needing speech-and-language intervention, they may get help with syntax. But regular classroom teachers rarely get the training or instructional materials that would lead them to focus on that problem or equip them to address it.¹

Yet a third reason syntax hasn’t gotten more attention as a cause of reading difficulties is that it’s been hard for researchers to distinguish the role of sentence-level comprehension from that of vocabulary, which largely reflects content knowledge. For one thing, knowledge of vocabulary often goes hand in hand with familiarity with complex syntax.

Another factor, though, is that the tests used by researchers have generally been constructed in a way that blurs different possible factors. If, for example, a sentence uses both complex vocabulary and complex syntax, it’s not clear which of those is the obstacle to comprehension, or what their relative importance is.

A New Study Isolates the Role of Syntax

But in a study published last year, and featured recently on the Literacy Through Research Substack, researchers managed to disentangle the two factors, along with decoding, by creating a test that involved simple vocabulary and complex syntax. Using a sample of 161 Danish sixth graders, the researchers give the students a sentence like “The cat that the rat had bitten played on the ship,” which they were then asked to repeat verbatim. A “whodunit” part of the test gave the kids sentences like “George was kicked by Sam under the table.” They were then asked who did the kicking.²

Contrary to what some previous studies had found, the Danish researchers determined that some children who had strong vocabularies weren’t able to parse complex sentence structure, and vice versa. That indicates that vocabulary and syntax comprehension are indeed two separate factors.

In addition, the study found that syntax comprehension was “by far the best predictor of reading comprehension,” exceeding vocabulary by a significant margin. That suggests, they wrote, that “the biggest obstacle for the majority of typically developing children in this age group is not understanding the individual words in texts, but using syntactic signals to connect the word meaning into sentence meaning.”³

Types of Complex Syntax

Several types of sentence structure can interfere with comprehension. In addition to the use of the passive voice, there are “noun phrases,” which add modifiers to nouns—like “the raging three-alarm fire” instead of just “the fire.” As sentences get longer, with multiple clauses, it becomes harder to connect the subject to the appropriate verb. Even a relatively short sentence can pose a problem if it inverts typical English word order—for example, “It could have been her tone of voice that her boss reacted to.”⁴

This kind of syntax shows up increasingly as students progress through grade levels, especially in expository texts in subjects like social studies and science. It also appears frequently in the real world.

A study done in 1982 found that the average sentence in a newspaper editorial was 20 words long and contained three clauses. Sentences may have gotten somewhat simpler since then, but it’s still not hard to find a complex sentence in a newspaper—like this one I just came across in the New York Times:

Instead of promoting economic policies, Mr. Vance, along with several Republicans including Representative Tom Tiffany, who is running for governor, and Representative Derrick Van Orden, who is running for re-election in a purple district he narrowly won in 2024, focused on castigating Democrats.

It’s not hard to imagine someone who is unfamiliar with complex syntax losing the thread that tells you who is “castigating Democrats.”

What Teachers Can Do

What does this mean for classroom instruction? One thing it should not mean is just having students memorize the difference between the active and the passive voice or the names of different grammatical structures. That won’t be enough, and could even be counterproductive.⁵ What’s important for comprehension is whether students can actually grasp the meaning of a sentence. It’s possible to know, for example, the definition of a subordinating conjunction but not be able to understand a sentence that uses one.

Nor should this mean giving students lots of random sentences and having them practice converting them from active to passive, or adding or subtracting dependent clauses. Doing some of that makes sense when introducing a new syntax concept. But once students have the basic idea, it’s likely to work best if teachers, of any subject, weave syntax instruction into the support they provide to help students understand the texts they’re expected to read.

In other words, syntax instruction isn’t a sixth “pillar of early literacy” that reading teachers should add to the “big five,” adopting a check-the-box approach. Rather, it’s something that needs to be integrated across the core curriculum, and deployed increasingly as grade levels go up.

Exposing children to complex syntax should begin early, through both oral language and read-alouds. One study found that preschool children who had been exposed to more diverse sentence structures were better able to understand those structures than their peers who hadn’t. For some children, that sort of passive, incidental exposure will be enough. But most will likely need more explicit instruction.

Identifying Syntax Problems

The first step is to pinpoint when syntax is interfering with students’ comprehension. One of the premier researchers in this area is Cheryl M. Scott, a speech-and-language pathologist and professor emerita at Rush University Medical Center. In one article, she recalls a therapy session with a fourth-grader named John that produced an “aha” moment. The grade-level text they were working with read in part as follows:

Thousands of pioneers went to live in unsettled land between the Appalachian Mountains and the Mississippi River. This land was then known as the West. Land that was part of the United States but did not have enough people to be a state was called a territory. The land to the west of the Appalachian Mountains was divided into two territories.

At that point, Scott paused to ask John to write a question based on the text. He wrote, “Why was the appellation [sic] mountains divided into two parts?” Scott realized he had connected Appalachian Mountains to the verb divided, rather than the actual subject, the noun land, which was farther away from the verb.

Of course, an interventionist works with one student at a time, and classroom teachers don’t have that luxury. Students will inevitably vary in their understanding of syntax, as well as complex text in general, and it can be hard to uncover who in the classroom is lost. John, for example, is unlikely to have raised his hand to ask whether the subject of the sentence was Appalachian Mountains or land. For one thing, he thought he knew the answer.

But classroom teachers can tackle this problem too. When dealing with a text that is likely to pose challenges for students, it’s important for teachers to guide the whole class through the reading rather than to expect individual students to overcome syntax barriers on their own. And if a sentence appears that seems likely to pose a syntax challenge, teachers can pause to ask a question that reveals whether students have literally understood it.

Let’s say a science text includes this sentence, which uses a relative clause (in bold):

All insects that go through incomplete metamorphosis must shed their outer skeletons as they grow.

After reading the sentence aloud, the teacher could ask, “Do all insects shed their outer skeletons as they grow?”⁶ Students can answer orally, but if teachers want to assess the comprehension of every student in the class, written responses will work even better.

Using Writing to Teach Syntax

Writing, in fact, is probably the most powerful way to address syntax comprehension problems. If you explicitly teach students how to use constructions like appositives and the passive voice in their own writing, they’ll be in a much better position to understand those constructions when they encounter them in their reading.⁷

The sentence-level technique that has the most evidence behind it is sentence-combining, which involves giving students a series of short sentences and having them combine them into one longer one. But many students will also need explicit instruction in the various ways to do that, such as using dependent clauses.

The Writing Revolution 2.0, of which I’m a co-author, offers a number of strategies and activities designed to familiarize students with complex syntax. When embedded in the content of the curriculum, these activities can also improve retention of information, deepen students’ comprehension, and improve their analytical abilities.

No Silver Bullets, But …

Instruction in syntax isn’t a silver bullet for reading comprehension problems. Comprehension is far too complex a process to be susceptible to any one “bullet,” silver or otherwise. It’s also not something you can teach once—or just in the early grades—and then be done with. It’s always dependent on a mixture of decoding ability, background knowledge and vocabulary, and familiarity with complex syntax. Each of those components will interact in various ways, depending on the particular text and the individual student.

If students are reading about a topic that’s familiar, their knowledge can help compensate for gaps in their decoding ability and/or their familiarity with complex syntax, enabling them to make educated guesses about meaning. By the same token, though, explicitly addressing syntax comprehension can help students compensate for a lack of background knowledge—enabling them to understand and gain new knowledge from texts on topics that are not already familiar.

Teachers may not be thrilled to hear that there’s yet another aspect of reading they need to address, feeling they have their hands full already. But, as the authors of the recent Danish study point out, in some ways the crucial role of syntax in comprehension is good news.

Building knowledge and vocabulary is inevitably a slow process, because there’s so much of it that students need to acquire to become proficient readers. Vocabulary instruction can and should focus on words that are likely to pop up in academic or complex text repeatedly, but many words are specific to certain subjects.

Rules of syntax, on the other hand, are relatively limited in number. If teachers weave syntax comprehension into whatever texts they’re teaching, they may well find that students are better able to transfer those skills to new texts—and as a result are better able to learn.

1. The report of the National Reading Panel in 2000, which drew on “reading research,” made no mention of the role of syntax in comprehension.

2. The researchers chose to focus on sixth graders because, they explained, up to that age reading comprehension is largely dependent on decoding skill. Like English, Danish has a relatively “opaque” orthography, meaning that the same letters can be associated with a number of different sounds. That makes it more challenging to learn to decode than a language with a “transparent” orthography, like Spanish.

3. The designers of the SAT seem to have figured out the role of complex syntax in comprehension. On the Substack The Science of Human Writing, Katharine Beals notes that after reading passages were limited to 25 to 150 words, the test began to feature sentences with more complex—and sometimes “unreadable”—syntax, to increase the challenge.

4. These and several other examples of complex syntax are borrowed from the work of Cheryl M. Scott.

5. Traditional grammar instruction, focusing on rules and parts of speech, doesn’t actually result in better writing for many students. Some studies have even found that such instruction makes students’ writing worse, according to one meta-analysis.

6. This example is taken from Scott’s article, A Case for the Sentence in Reading Comprehension. Ideally, the curricula that teachers use will help them flag potentially difficult sentences and suggest ways to identify and address syntax comprehension problems—not only in English language arts classes but across subject areas. That, of course, would require curriculum designers to become more aware of the issue.

7. The passive voice is generally looked on with disfavor, and students shouldn’t be encouraged to use it too much in their writing. But there are times when it makes sense—for example, when the subject of the sentence is unknown—and it can help students understand a type of sentence construction they will inevitably encounter in their reading.