The Lexile Framework finds the right books for students by measuring readers and texts on the same scale Lexile measures are the global standard in reading assessment and are accurate for all ages, including first and second language learners May 14, 2018 · While Lexile measures correlate with other readability scores, they may be more precise (Wright & Stone, 2004). In part, this is because the Lexile tool analyzes each word in a passage, comparing it to a 600-million word corpus to determine vocabulary difficulty (Lexile, 2017). Apr 29, 2016 · Answered April 29, 2016. Typically... 25th to 75th Percentile looks as follows per grade. 1st Grade - Up to 300. 2nd Grade - 140 to 500. 3rd Grade - 330 to 700. 4th Grade - 445 to 810. 5th Grade - 565 to 910. 6th Grade - 665 to 1000. 7th Grade - 735 to 1065.