There are two easy ways to confirm that a books is part of AR. One way is to look in the HPL catalog.
In the entry under the heading Program Information, you see "Accelerated Reader AR LG 2.2 0.5 107422."
In the entry under the heading Program Information, you see "Accelerated Reader AR LG 2.2 0.5 107422."
This entry tells you three things: The interest level of the book, the title's reading level, and the number of the associated AR quiz. In the example above, LG indicates the interest level is "lower grades." In other words, K-3rd kiddos will likely enjoy the material. MG = middle grades (4th-8th), MG+ = middle grades plus (6th and up), UG = upper grades (9th-12th).
Next you see the number 2.2. This means that the text could be read independently by a student whose skills are at the level of a typical second-grade student during the second month of school.
The next number indicates the number of AR points that title is worth. (Teachers often have a target number of points the students are working to earn in a particular grading period.) The 0.5 in the example tells you that this picture books is worth half an AR point.
Finally, we see the number 107422. This is the test number of the AR quiz associated with this book.
Another place to find this information is at arbookfind.com. (There is a link to this site in the Reference section of this blog.) Click on "Librarian" and hit submit. You will see a search tool that allows you to type in a title; the site will then generate an entry that gives you the same information in a clear format. IL = interest level and BL = book level.

