Lexile by 170L to 545L

Two main factors influence reader engagement – how interesting the books are and how difficult they are to read. Lexile measures are indicators of book difficulty or text complexity. MetaMetrics’ Lexile Framework for Reading calculates a book’s text complexity based on word frequency and sentence length. According to the Common Core State Standards, students should read books at a Lexile level of 770 or above by the time they are in Grade 4; a Lexile level of 955 or above by the time they are in Grade 6; and a Lexile level of 1080 or above by the time they are in Grade 9. However, some books may have a lower Lexile level but have a highly complex narrative due to their content and length. For this reason, the Common Core State Standards encourage teachers to consider other criteria, such as the plot and character themes and book-length when selecting books for their classroom.