Created by MetaMetrics, an educational research company, a Lexile measure is a representation of one of two things: a text's difficulty or a reader's proficiency. Lexile measures can be used to match students to texts that will challenge but not overwhelm them.

A Lexile measure is generally represented by a number followed by the letter L, e.g., 1050L.

Let's take a deeper look at the two kinds of Lexile measures: text measures and reader measures.

Text Measures

A Lexile measure of a text tells you roughly how challenging the text is—and only how challenging the text is. Lexile measures say nothing about the text's quality or its content. A terrible book could have a sky-high Lexile measure, and a great book might have a relatively low Lexile measure.

When we talk about a text's difficulty in terms of its Lexile measure, we need to keep in mind that we're talking about only how difficult the text is to parse. Some books present complex ideas and themes in simple language; in fact, many great works of literature do just that.

For example, Of Mice and Men has a Lexile measure of 630L. A recent MetaMetrics study found that most second graders in the United States can read at a range between 425L and 790L. Of course, assigning Of Mice and Men to second graders seems absurd—and it is. The language used in Of Mice and Men is relatively easy to comprehend, but the concepts it presents are tougher.

When choosing texts for your students, don't rely solely on Lexile measures. Make sure you're choosing texts that have grade-appropriate content as well.

Many of the books we sell at Prestwick House have Lexile measures assigned to them. When you look at a book's product information page, look for the sidebar on the right side of the screen to find the book's Lexile measure.

The sidebar on the Of Mice and Men product detail page shows the book's Lexile measure.

Reader Measures

Lexile measures can also be applied to students. Reader Lexile measures are determined by student performance on end-of-year reading assessments.

Not all states have opted into the Lexile measure program. You can check whether your state has opted in—and, if your state has, find out how to assess your students' Lexile measures—by clicking here.

How Do Text Measures and Reader Measures Match Up?

If a reader's Lexile measure matches that of the text they're reading, the reader can be expected to comprehend approximately 75% of that text. Of course, with support from you, that percentage increases.

So, if a reader's Lexile measure has been recorded at 630L, they can be expected to comprehend approximately 75% of Of Mice and Men, which also has a 630L Lexile measure.

As a student's Lexile measure increases, this percentage increases as well. The percentage increase is not on a linear scale; a student with a Lexile measure of 880L (an increase of 250L) can be expected to comprehend 90% of Of Mice and Men, while a student with a Lexile measure of 1130L (another 250L increase) can be expected to comprehend 96%. The law of diminishing returns applies here.

As a student's Lexile measure decreases, however, the corresponding effect on comprehension is much more pronounced. A student with a Lexile measure of 380L (a 250L decrease) can be expected to comprehend only 50% of Of Mice and Men. A student with a Lexile measure of 130L (another 250L decrease) can be expected to comprehend 25%.

Clearly, assigning students texts with Lexile measures above level is a dangerous proposition, as their ability to comprehend texts drops precipitously as text difficulty increases.

For this reason, it's considered a best practice to assign readers texts with Lexile measures no higher than 50L above their personal measures.

Lexile Measure and the CCSS

The Common Core State Standards expect students to reach a certain level of reading proficiency in each grade to make sure they're on the path to be college- and career-ready by their high school graduation.

On the MetaMetrics website, you can see the ranges of Lexile measures for typical readers (50th to 90th percentile) at each grade level. You can also see the ranges of Lexiles the CCSS expect students to be able to read.

In every grade, the range of Lexile measures demanded by the CCSS is higher—in other words, the lower end of the CCSS range is higher than the lower end of the typical student range, and the higher end of the CCSS range is higher than the higher end of the typical student range. This means that under the CCSS, the typical student will be asked to read more difficult texts than previously.

It may be tough to reconcile this with the best practice recommended above—assigning students texts with Lexile measures no higher than 50L above their personal measures.

But students often develop throughout the school year, and it isn't unreasonable to expect a student's Lexile measure to increase with time and practice. By gradually increasing the difficulty of assigned texts throughout the school year, you can help your students reach these higher CCSS Lexile measure ranges.

You Are of Paramount Importance

Because these CCSS Lexile measure ranges are higher, your support is more important than ever to your students. Luckily, there are many ways you can help.

Use Vocabulary Lists

Something as simple as giving your students a list of vocabulary words and definitions prior to reading can help increase their comprehension of a text.

Use Direct Vocabulary Instruction

Teaching vocabulary independent of other subject areas is a great way to expand your students' lexicons and increase the likelihood that they'll understand challenging texts they'll read in the future.

Choose Texts With Sidebar Annotations

Some texts (especially rigorous nonfiction and Shakespearean works) are challenging for adults, let alone students. Choosing books that add sidebar annotations to these texts can give your students an advantage. These sidebar annotations should clarify tough passages in plain language, alert students to important historical context, and explain arcane allusions, among other things.

Encourage Independent Reading

It stands to reason that the more your students read, the better at reading they'll become. Encourage them to seek out books about subjects they enjoy. Keeping a small library in your classroom is also a great idea; a student may see a title that piques his or her interest.

Questions? Get in touch!

If you have any questions about Lexile measures or need help finding the right books for your students, feel free to email us at info@prestwickhouse.com. We're happy to help.

METAMETRICS®, the METAMETRICS® logo and tagline, LEXILE®, LEXILE® FRAMEWORK, LEXILE® ANALYZER and the LEXILE® logo are trademarks of MetaMetrics, Inc., and are registered in the United States and abroad. The trademarks and names of other companies and products mentioned herein are the property of their respective owners. Copyright © MetaMetrics, Inc. All rights reserved.