A Lexile measure is a valuable piece of information about either an individual’s reading ability or the complexity of a text. The Lexile measure is shown as a number with an “L” after it (for example, 880L is 880 Lexile). A Lexile reader measure can range from below 200L for emergent readers to above 1600L for advanced readers. Readers who score below 0L receive a "BR" for Beginning Reader. A Lexile text measure is based on the semantic and syntactic elements of a text. Many other factors affect the relationship between a reader and a book, including its content, the age and interests of the reader, and the structure of the text. The Lexile text measure is a good starting point in the text-selection process, with these other factors then being considered by LightSail's custom curation experts and in-app personalization.
Please find more research behind the Lexile Framework by visiting MetaMetric's website here: https://lexile.com/research-and-publications/research-on-products/.