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Teaching Complex Text: Why Look at Word Frequency?

Posted by Elfrieda H. Hiebert on 21 June 2012

A webinar version of this content is also available:
Teaching Complex Text: Why Look at Word Frequency

For the first time in a standards document, the Common Core State Standards (CCSS) has a standard—Standard 10—devoted solely to ensuring that students increase ability to read complex texts. The Common Core used Lexiles to identify a quantitative staircase of text complexity through which students need to pass.

CCSS Staircase of Text Complexity

How are teachers supposed to use this information? Lexiles, like most readability systems, are good for sorting large groups of texts. But that isn't what teachers do. Teachers typically have particular texts that they need to teach. What does it mean for a teacher to teach a text with a 700 Lexile? And why do Grapes of Wrath,1 a text taught in high school, and Where do Polar Bears Live,2 a text for early readers, have a similar Lexile—around 700—which is toward the end of the CCSS second-third grade step in the text complexity staircase. These Lexiles don’t make sense until you examine what makes up a Lexile—sentence length and word frequency.

Text Lexile Sentence Length Word Frequency
Grapes of Wrath 680 9.2 3.46
Where do Polar Bears Live? 700 10.4 3.53

This information helps to explain this strange sorting of text. Grapes of Wrath has shorter sentences, on average, than Polar Bears. This makes sense. After all, there is a great deal of dialogue in a novel like Grapes of Wrath, while Polar Bears is an informational book without dialogue. Sentences in dialogue are usually short. But when it comes to vocabulary, Grapes of Wrath is harder. The lower the word frequency score, the harder the vocabulary in the text.

The information on sentence length and word frequency is a great way for teachers to start zooming into what makes text complex. That is why—in teachers’ guides in Scott Foresman Reading Street Common Core3—this information is given for each focus text. Teachers use this information to begin delving into what makes a text more or less complex for students. Both parts of a Lexile—sentence length and word frequency—are important. But word frequency or vocabulary is especially critical, since it is one of the strongest indicators of a text’s difficulty.

And that is precisely why word frequency information is included in the Reading Street Common Core edition at the front of every unit on a page like the one below. The word frequency measure gives a sense of how many rare words are in a text. Rare words are ones that occur once or a few times for every million words of text. The word frequency measure doesn’t tell you exactly what the rare words are or exactly how many there are. But it does serve as a road sign—either “caution ahead” or “ok to maintain the speed limit.”

Text Complexity Measures for Dear Juno

The range in word frequency is given in the table below. High numbers mean fewer rare words; low numbers mean more rare words in texts. Let me illustrate how a teacher would use this information with two texts from the Common Core exemplars (from Appendix B of the CCSS): Telescopes from the end of the scale where texts have many rare words and The Treasure from the top end with few rare words.

Telescopes, a text identified by the CCSS as an exemplary informational text for Grades 4–5, has a Lexile of 1070. Sentence length is 12.7 (moderate for elementary text). But the word frequency is 3—which indicates that the amount of rare vocabulary is great. A sample of the text illustrates the kind of vocabulary in the text:

“Non-optical telescopes are designed to detect kinds of electromagnetic radiation that are invisible to the human eye. These include radio waves, infrared radiation, X rays, ultraviolet radiation, and gamma rays.”4

As this illustration shows, there are numerous technical, complex words. In fact, the number of rare words is so great and their meanings so complex, a teacher might decide that this text is simply not appropriate for fourth or fifth graders. But if the text is a mandated one in a curriculum, the teacher might decide to design a lesson specifically around the vocabulary. For this lesson, a handful of pictures of telescopes gotten from different websites could be especially useful.

 Word Frequency Description A Common Core Exemplar
Few rare words 3.9–4.0+ A handful of rare words in entire text—often synonyms for words students know. The Treasure
(Grs. 2–3)
  3.7–3.8 Approximately 2 rare words per every 100 words in a text. The Raft
(Grs. 2–3)
3.5–3.6 2–3 rare words per every 100 words, some synonyms for known concepts, some representing new concepts/places/people. Throw Your Tooth on the Roof
(Grs. 2–3)
3.3–3.4 3–5 rare words per every 100 words—some representing unknown concepts. Bat Loves the Night
(Grs. 2–3)
Many rare words (Usually very technical) 3.1–3.2 4–6 rare words per 100 words—almost all representing unknown concepts. About Time
(Grs. 4–5)
3.0 and below A large number of rare words (as many as 7 or more words per 100 words), usually highly technical words in sciences. Telescopes
(Grs. 4–5)

At the opposite end of the scale is a text in the category with fewest rare words: The Treasure with a word frequency of 3.9. This text is a CCSS exemplary narrative text for the grade 2-3 step on the text complexity staircase, with a Lexile of 650 and average sentence length of 11.9. Looking at the book confirms a sprinkling of rare words—not many, but a handful, as illustrated in this sentence:

“In thanksgiving, he built a house of prayer, and in one of its corners he put an inscription: Sometimes one must travel far to discover what is near.”5

For many second graders, the level of vocabulary will be manageable. A word such as inscription can be explained easily (e.g., a label with writing). But this sentence is a reminder of another piece that goes into making up a Lexile: sentence length. An average of 12 words per sentence means that there are some long sentences in the texts. This sentence also reminds the teacher that a text’s genre, in this case, a fable, contributes to text complexity. The vocabulary may not be a problem for proficient second graders but the complex sentences and the type of text might be.  Such information is located in the qualitative analysis that is part of the Reading Street Common Core summary.  Here teachers can consider the background knowledge and other text features. But the process of zooming in on what is critical to teach in texts can begin with the quantitative information—especially on vocabulary or word frequency. By providing this information, Reading Street Common Core aids teachers in knowing how and what to teach to increase students’ capacity with complex texts.

1 Steinbeck, J. (1939). Grapes of wrath. New York, NY: Viking.

2 Thomson, S.L. (2009). Where do polar bears live? New York, NY: Collins.

3 Afflerbach, P., et al. (2013). Scott Foresman Reading Street Common Core. Glenview, IL: Pearson.

4 Ronan, C.A. (2010). Telescopes. In The new book of knowledge. New York, NY: Scholastic.

5 Shulevitz, U. (1978). The treasure. New York: Farrar, Straus, & Giroux.