Lexile Guide

The Ins and Outs of The Lexile Framework® for Reading

If a child is disadvantaged as a reader, he or she is disadvantaged as a learner and this can have a significant impact on the opportunities available to him or her beyond the school years. Giving children access to books that will engage and inspire them is a powerful way to spark interest in reading and, once ignited, their passion for reading will last a lifetime.

The Lexile Framework in a nutshell


                                                                                           The Lexile Framework® for Reading is a scientific approach to measuring reading ability and text difficulty on the same scale, using the same measuring unit called a Lexile®. A Lexile measure is a number followed by the letter "L". It can range from below 200L for beginner readers and beginning-reading text to above 1700L for more advanced readers and text.

OK, but why is it so useful?

The impact of Lexile measures can be huge but the process is actually pretty simple:

Step 1: A child receives a Lexile measure from a reading assessment or program.

Step 2: This measure is entered into the Lexile Book Database along with information on books and topics in which the child takes an interest.

Step 3: Individual book titles from the Lexile Book Database are mapped to the child.


More on how this works later, but, for now, let’s look at what this means in practical terms. For years, we have connected children with books and other learning materials based on age or school year.

This is all very well for children who read at the “average” level for their age. But for children above or below that level, this all too often leads to frustration and a lack of motivation because the books are either too difficult or not challenging enough.



Lexile measures enable teachers and parents to select books and other reading materials that are targeted to a child’s individual reading ability. As such, it is an immediately actionable piece of data – not just another score or test result. By taking the guesswork out of picking the "right" books, parents are able to select books with confidence, safe in the knowledge that the child will not be disheartened by reading material that is too easy or beyond his/her ability.

And by personalising literacy in this way, the Lexile Framework goes hand in hand with the growing need for personalised learning.

Who’s behind it all?

The Lexile Framework for Reading was developed after 20 years of research by psychometricians at MetaMetrics®, Inc., a privately held, US-based educational measurement company.

The company’s research was initially funded with grants from the National Institute of Child Health and Human Development, part of the National Institute of Health. Today, MetaMetrics continues to pioneer scientifically based measures of student achievement that link assessment with instruction, foster better educational practices and improve learning by matching pupils with materials that meet and challenge their abilities.

Lexile measures are now the most widely adopted measure of reading ability in the United States, with more than 28 million measures being reported annually. This success has helped encourage the introduction of the Lexile Framework into other countries.

GL Assessment is now working with MetaMetrics to make the Lexile Framework available in the UK. But while the Lexile scale can be easily transported across the Atlantic Ocean, other aspects – certain titles in the book database, for example – were less appropriate for the UK market. Therefore, much of the last year has therefore been spent moulding the Lexile Framework to UK interests and teaching curriculums, ensuring the resource is right for UK schools and children.

So how does a child get a Lexile measure?

In US schools, major standardised reading tests report a Lexile measure in their results. In the UK, GL Assessment’s renowned Progress in English (PIE) test now does the same.


Once a child has a Lexile measure, he or she can search for books in his or her Lexile range - about 50L above and 100L below his or her Lexile measure. When the child's Lexile measure or range is entered into the Lexile Book Database, along with information on books and topics in which the child takes an interest, a bespoke reading list is produced with titles that are designed to meet and challenge the child’s unique abilities, interests and goals.

Matching a reader’s Lexile measure to a text with the same Lexile measure leads to an expected 75% comprehension rate. This is the optimal reading capacity – not too difficult to be frustrating, yet difficult enough to be challenging and to encourage reading progress.

If a child attempts material above his or her upper Lexile range, the level of challenge is likely to be too great for the student to be able to construct much meaning from the text. Similarly, material below the lower Lexile range will provide the child with little comprehension challenge.

While children should be encouraged to move on to more demanding material as their skills develop, it is not necessary for them to advance to a higher Lexile measure with each new book. By reading several titles at one Lexile measure, young readers can build confidence and comfort in their degree of reading comprehension before tackling books with a higher Lexile.

And how accurate is a child’s Lexile measure?

Every time we obtain a Lexile measure for a child, we are looking at an estimate. If we repeatedly measure a child many times over a short interval, the measurements will not all be the same. In this respect, it’s like getting your blood pressure measured!

Variability in measurement can occur over time due to various factors, such as the test conditions or the child’s health and well-being. The typical amount of variability is about 70L for any given test administration. Multiple measurements will reduce this error and, therefore, are encouraged for more precise measurement.

Back to Progress in English

                                                                               Before we look at the science behind the Lexile Framework, let’s go back to Progress in English for a moment. PIE is one of our most popular literacy tests, providing rich diagnostic information about pupils’ ability in English to help teachers quickly identify strengths and needs. It is available in both paper and digital format. More information can be found at www.gl-assessment.co.uk

In addition to the new Lexile report, PIE Digital users also can benefit from built-in letter templates that can be used to communicate with parents about children’s reading goals and progress.


Now for the scientific bit…




Based on decades of research, Lexile measures are based on two well-established predictors of how difficult a text is to comprehend, namely semantic difficulty (word frequency) and syntactic complexity (sentence length).

In order to establish the Lexile measure of a book or article, the text is split into 125-word slices. Each slice is compared to the nearly 600-million-word Lexile corpus, taken from a variety of sources and genres, and the words in each sentence are counted.

The next step involves putting these calculations into the Lexile equation and the resulting Lexile measures for each text slice are then applied to a measurement model called the Rasch psychometric model which calculates the Lexile measure for the entire text.  

How does a book get into the Lexile Book Database?

The Lexile Book Database currently holds over 115,000 fiction and non-fiction titles from over 150 US publishers, including Pearson Education and Scholastic. And with more and more books being added on a regular basis, the Lexile Book Database is continually growing.

With tens of thousands of titles already, the UK version of the Lexile Book Database is hard at work catching up! Usborne was the first publisher to jump on board and an initial 200-plus Usborne books now have a certified Lexile measure, with more to come. Other key UK publishers are expected to follow suit soon.

If you are a publisher interested in obtaining a Lexile measure for your titles, more information can be found in the Publisher section of this website, or contact Graham Taylor on 0208 996 3333.  You will be surprised how quick and easy a process it is!

How can Lexile measures be put into practice in the classroom?



The most obvious answer here is to use the Lexile Book Database to create a suggested reading list for every child that meets his or her unique reading ability and interests. 

However, Lexile measures can influence teaching and learning in many ways too–see below for examples of how.

  • The Lexile Framework is a useful means of communicating with parents in a clear, non-judgmental way about children’s reading goals and progress. As such, it is an ideal way of connecting learning in school with learning at home, by providing parents with actionable advice for building literacy skills.
  • Teachers can easily keep track of children’s progress on the developmental Lexile scale, enabling reading ability to be monitored over time and providing information on when intervention and additional support is required.
  • By comparing the range of pupil's Lexile measures to the Lexile measures of books available in the school library, library collections can be analysed and developed to more fully meet the needs of all pupils.
  • And last but not least, teachers can use the Lexile Analyzer® to obtain Lexile measures for their teaching materials, and then compare these measures to each child’s Lexile measure. Children above or below the average can then be connected with more ability-appropriate content, enabling every pupil to stay on track.


Don't hesitate to contact the Lexile team at    GL Assessment directly on 0845 602 1937 or e-mail us to get your questions answered or to arrange a FREE NO-OBLIGATION DEMONSTRATION at your school or organisation.

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Regardless of whether you are an advocate or adversary of age-banding, it is vital that parents get the support they need to help boost their children's reading skills. A Lexile measure can provide this support - whether it stands beside age guidance on books or instead of.
Andrew Thraves, Publishing Director, GL Assessment
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