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The Lexile^® Framework for Reading is a scientific approach to measuring reading ability and the text complexity of reading materials. The Lexile scale is like a thermometre, except rather than measuring temperature, it measures a text’s complexity and a reader’s skill level.

When these two measures match, a targeted reading experience occurs. Students who read at the right levels experience more reading achievement and growth. Renaissance partners with the creators of the Lexile Framework, MetaMetrics^®, Inc., to bring Lexile measures into Renaissance Accelerated Reader^® .

How can Lexile measures guide students to appropriate books and articles?

The Lexile Framework assesses both sides of reading development: the reader and the material being read. When a student chooses texts 100L below to 50L above his or her reported Lexile reader measure, a targeted reading experience can occur. The Lexile reader measure describes an individual’s reading ability. The Lexile text measure describes the semantic and syntactic features of a book, article, or text. Both Lexile reader measures and Lexile text measures are reported on the Lexile scale and are represented by a number followed by the letter “L” (i.e., 1000L).

Lexile measures are quantitative measures that provide insights into the difficulty of the words in a book or article. It is, however, only one of three components associated with text complexity. The other two are qualitative measures (i.e., content, themes, and maturity level) and reader/task considerations. Lexile measures do NOT measure age appropriateness, the book quality, the book’s theme, or other characteristics of the book. For example, The Grapes of Wrath is a rather simple read, but it may have a theme that is inappropriate for a certain age group.

All books with Accelerated Reader quizzes include an ATOS level, a Lexile measure, and an interest level (i.e., lower grades [K–3], middle grades [4–8], middle grades plus [6–8], and upper grades [9–12]. Teachers, librarians, and parents may want to consider all three components when matching students with books.

ATOS and Lexile measures are both valid, reliable measures of text complexity that provide a basis for matching students to reading materials. As with all readability formulas, the resulting value is an estimate of the text’s understandability.

How is a Lexile measure obtained?

To obtain a Lexile measure for a book or article, text is split into 125-word slices. Each slice is compared to the nearly 600-million word Lexile corpus, which is taken from a variety of sources and genres, and the words in each sentence are counted. The lengths of sentences and the difficulty of the vocabulary are examined. These calculations are put into the Lexile equation. Then, each slice’s resulting Lexile measure is applied to the Rasch psychometric model to determine the Lexile measure for the entire text.