I have begun the task of putting Lexile measures on book spines in the media center. I am not color coding and I am not filing by reading levels. I am also not putting Lexile numbers beside or near Call Numbers. 
Students will see Lexile codes on top of book spines. I am putting a blank label on books that do not have a Lexile measure (simply to help me  in the process of this task). 
This is the time of year that I especially miss an assistant. 
While most of our books already have Lexile information on a label inside the front cover, the spine code will assist students who browse for reading levels without using the automated card catalog or the Lexile website to search for books within their Lexile range. (Students are able to search by reading range for Lexile and Accelerated Reader in Surpass Safari).
For other media specialists who may be interested labeling books for Lexile, I am including a document that shows step-by-step instructions. 
It is, however, extremely important for a student to know how to find a book using the automated card catalog. He should know that the Call Number is the very key to something called the Dewey Decimal System. A Call Number with FIC and three letters is linked to a book in the fiction section, which is filed alphabetically using the last names of the people who write books (who are called authors). A Call Number that begins with a number, like 921 and three letters, is a non-fiction book. The non-fiction section is filed in categories from 000 to 999 primarily and then by author last names. (921 WAR, 921 WAT... 976.8 BUR). 
According to Lexile.com, the Lexile code provides information about a book "that relates to its developmental appropriateness, reading difficulty, and common or intended usage." The two text characteristics that determine a Lexile measure are "Word Frequency" and "Sentence Length."
The Lexile codes are:

• AD: Adult Directed
• NC: Non-Conforming
• HL: High-Low
• IG: Illustrated Guide
• GN: Graphic Novel
• BR: Beginning Reading
• NP: Non-Prose

For information on Lexiles, go to http://Lexile.com. I have included a photo of books with Lexile spine codes in the document.