PROBLEM with “Lexile” levels for informational texts

Please be careful when using quantitative measures like Lexile to determine whether an informational text is appropriate. Below I make the case for why this is a problem by comparing two books with similar Lexile levels. This is an excerpt from the manuscript for my next book which is on what makes informational texts complex!

nic bishop spiders

Quantitative analyses of texts like those available at Lexile.com are limited in the number of “parts” that can be addressed. These parts include number of words in the text, complexity of the sentences, and presence of challenging vocabulary. Why is this a problem? Let’s compare the Lexile level for two informational texts. The first is Nic Bishop’s Spiders (2007). Bishop’s purpose is to describe spiders’ physical attributes and behaviors. While the text has challenging vocabulary like tarantulas, abdomen, and camouflaged, the running text and photographs (for which Bishop is notable) scaffold for understanding by younger students. Developmentally, this book could be read aloud to students in the primary grades and be read independently by second to third graders who are reading at transitional to early proficient reading levels. The publisher, Scholastic, lists this book as appropriate for preschool through third grade (store.scholastic.com). According to Lexile.com, the Lexile for Spiders is 820.

stronger than steel

Now let’s consider another text about spiders, Stronger Than Steel: Spider Silk DNA and the Quest for Better Bulletproof Vests, Sutures, and Parachute Rope (Heos, 2013) which is a book in the Houghton Mifflin Scientists in the Field series. The author’s purpose in the book is to explain how a team of scientists is genetically implanting goats with the DNA of a spider called the golden orb weaver. The milk from these goats, as a result, contains proteins that can be spun into an amazingly durable silk. With an audience of middle school to early high school readers in mind, Heos reports on the concepts of DNA and genes, on different golden orb weavers and the properties of their silk, the “spider goats” involved in the experiments, the team of scientists involved, as well as how they go about doing this work. Just from my description of these two author’s purposes, you can surmise the difference in the complexity of this text. The publisher, Hougton Mifflin, lists this book as appropriate for grades 7-10 (www.houghtonmifflin.com). And yet, according to Lexile.com, the Lexile for the text Stronger Than Steel is 860, not a significant increase in difficulty from that of the much simpler text Spiders (Bishop, 2007).

This contrast is not simply a blip on the part of Lexile.com, but a reverberating problem when considering whether informational texts are appropriate for particular readers. Human readers make the best assessors of appropriate informational texts for our students. 🙂

 

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