Reading Comprehension Depends on Content Knowledge


Michael C. Zwaagstra March 13, 2018

Walk into an elementary school classroom and you will probably see a lot of books on the shelf. Take a closer look and you will often find a coloured dot, a number, or a letter on each book’s spine. Those dots, numbers, and letters show the reading level of each book.

Books are assigned these levels so students choose books that will challenge them without being too difficult for them. Instead of having the entire class read the same book, students pick books from their designated reading levels. Levelled libraries make it possible for students to find the best books to read. At least that is the theory, but the reality may be somewhat different.

In order for students to read a text effectively they must be able to do two things—decode the individual words and comprehend the sentences and paragraphs. Too often we focus on how students decode words (the ongoing phonics vs. whole language debate), but in that debate we neglect the importance of reading comprehension. A student may be able to “read” every word on a page and yet not understand what the text actually means.

I used to be an elementary school teacher so I remember doing running records with my students to assess their reading levels. However, it didn’t take long before I noticed that my students performed much better on the comprehension questions after reading an article about a sports game than after reading an article about Dr. Norman Bethune, the Canadian medical doctor who went to China in the early twentieth century, even though both articles were officially at the same reading level. The question is “Why?”

The problem with reading levels is they focus on quantitative factors such as word complexity and sentence length but fail to account for the important connection between specific content knowledge and reading comprehension. A student may be able to decode every single word in an article about Dr. Norman Bethune, but still be clueless about the article’s meaning since they know virtually nothing about Communism, the Second Sino-Japanese War, or blood transfusions.

In contrast, most students will breeze through an article about a hockey game because they already know how the game works. They have no difficulty understanding phrases like “high-sticking,” “pulling the goalie,” and “killing a penalty.” However, imagine how hard it would be for someone who had never heard of ice hockey before to understand an article that used these phrases. Prior knowledge about this Canadian game is actually more important to reading comprehension than the length and complexity of the words and sentences in the article.

Thus, it is clear that reading levels by themselves do a very poor job of matching students with the proper books to read. In fact, that was the finding of a recent peer-reviewed research study that appeared in the April 2018 edition of Reading and Writing. In this study, James W. Cunningham, Elfrieda H. Hiebert, and Heidi Anne Mesmer examined two of the most widely used reading level classification systems, the Lexile Framework and the Flesch-Kincaid Grade-Level Formula.

Both of these systems have the aura of precision because it is relatively easy to calculate the average number of syllables in words, mean sentence length, and word frequencies. However, precision does not guarantee validity, particularly when it comes to reading comprehension. Cunningham, Hiebert, and Mesmer, in fact, found that “these two text tools may lack adequate validity for their current uses in educational settings.”

By placing reading level stickers on their classroom library books, teachers may be inadvertently preventing students from reading the books that would benefit them the most. Students who know a lot about a particular topic can read almost any book about it, no matter its assigned reading level. Conversely, students who know little about a topic will struggle with books at even the simplest reading levels.

This means that schools must place a much stronger emphasis on the acquisition of subject-specific content knowledge, particularly in the early grades when students are building up their general knowledge base. Instead of spending hours working on generic reading comprehension “strategies”, students should learn as many facts as possible about science, history, and the world we live in today. Time spent classifying books into reading levels would be much better spent building up the students’ background knowledge.

The more knowledge students acquire, the more they will be able to learn in the future. This is how we can help our students become stronger readers and gain a better understanding of the world in which we live.