NWEA has partnered with MetaMetrics®, Inc., the developer of The Lexile Framework® for Reading. A Lexile range is a score (displayed as a 150-point range) resulting from a correlation between NWEA’s RIT score and the Lexile scale that helps identify reading material that is at an appropriate difficulty level for an individual student. The 150-point Lexile range is included on NWEA’s Individual Student Progress Reports. It allows educators and parents to find books, periodicals, and other reading material that should stimulate a student to new learning while rewarding their current reading abilities.

A Lexile measures syntactic complexity–the number of words per sentence. We know that longer sentences are more complex and require more short-term memory to process. A Lexile also measures semantic difficulty–a measure of vocabulary. This measure looks at the frequency of words in a text compared to a body of over 400 million words. This is the largest repository of text in the world and is quickly approaching 500 million words.

It is very important for parents to keep in mind that Lexile does not evaluate genre, theme, content, or interest. Even though a student might be able to read books at a certain Lexile, the content or theme of the text may not be appropriate for that particular student because of his or her age or developmental level. Also, a student may be able to read more difficult content if it is an area of interest for that child since he or she may already be familiar with some of the vocabulary necessary to comprehend the text.