Both ALA’s American Association of School Librarians (AASL, a division of ALA) and the National Council of Teachers of English (NCTE) have registered concerns in using such programs, pointing out the limitations and presumptions inherent in them, in determining what children of a certain age "should" read. Perhaps the most well-known of these programs for "leveled books" and "guided reading" are Accelerated Reader by Renaissance Learning and the Lexile Framework for Reading.
School Library Journal, April 2006 "Labelling and Rating Systems: An Interpretation of the Library Bill of Rights from ALA's Office for Intellectual Freedom" (excerpt)
''I would like to organize sections of the library using reading level designations, such as those supplied by Accelerated Reader. Is this okay?''
While knowing the reading level of a book can assist library users, organizing a library via these labels can pose a psychological barrier for users who do not know their reading level. Many will feel that they should not utilize those resources. Users who do know their reading level may feel compelled to only select resources from their reading level. This will result in users not utilizing the full scope of the library collection.