There is no official body that assigns a reading level to books. Most often, a book’s reading level is determined by the book’s publishers. A book review or publisher’s description is the original source for a book’s reading level designation. The book publisher will assign the book to a certain category for marketing purposes such as picture book, easy reader, early chapter book, middle grade fiction or nonfiction, or young adult fiction or nonfiction. They will sometimes describe the book as pertaining to a certain age or grade level, such as “for ages 5-8” or “for grades 5-9.” Sometimes these publisher descriptions are wildly inaccurate as to the reading level and/or interest level of a particular book.
Picture books are intended for preschool and primary-age children, but they aren’t necessarily meant to be read by those children. Instead, although the vocabulary may be somewhat controlled for a younger audience, picture books are meant to be read aloud by adults. Therefore the vocabulary and sentence structure of the text is written for fluent, adult readers. Easy or beginning readers, in contrast, have a controlled vocabulary, sometimes with larger print size and simply structured sentences. Different publishers assign reading levels to their beginning reader series, within the series, such as Level A, B, or C or Level 1, 2, or 3.
The publisher-assigned genre designation is also confusing at higher age levels because “middle grade” (MG) and “young adult” (YA) can refer to the reading difficulty level of a book or the maturity level of the intended reader or both.
“Middle grade novels are typically for the ages of 8–12. They are usually shorter, and are significantly less mature and complex in theme and content than YA. YA novels are for ages 12–18, and tackle more mature and adult themes and content. Middle grade novels usually feature protagonists between the ages of 10 and 13, whereas young adult novels usually feature protagonists from 14 to 18” (Wikipedia).
The designation of middle grade or YA, then, generally says nothing about the actual difficulty in the reading level of a book.
Sometimes reading specialists, children’s librarians, or school librarians assign their own reading levels to books in their own schools or libraries. In addition, there are many different leveling systems and reading programs, usually provided by publishers or sellers of reading curricula, for determining the reading level of a book.
Biblioguides, the online book database, assigns a reading level to the books on the website. Their books are classified as Emerging Reader, Lower Beginner, Upper Beginner, Lower Intermediate, Upper Intermediate, or Advanced. It is then up to the librarian or parent to decide whether the intended reader is a lower beginner or upper beginner, intermediate or advanced.
All of these tools and genre/grade level designations depend on generalizations about the typical reading ability and maturity level of children who are of the same age or in the same grade level at school. But of course, one eight-year-old may be reading much more difficult material than another. In addition, a fifth grader and an eighth grader who are both “middle grade readers,” even if they are reading at the same comprehension level, may be interested in and have the maturity to enjoy far different books.
One simple way to determine if a book is at an appropriate reading level for a given child is the “five finger rule.” Have the child begin reading a chapter aloud, and put down one finger each time he struggles with a word. If he reaches the end of the page before you get to five fingers, the book is written at a comfortable level for independent reading. In the end, a librarian, teacher, parent, or the child himself is the best person to decide if the reading level of a specific book is appropriate for a specific child.
Read more about reading levels for children and for children’s books