But there are some catches. As longtime teachers, we have seen how students — who are tested and assigned a level — internalize those categories. Students have told us, “I am a G reader” (an example of another reading-level system). Then they share how it makes them feel to be a “G reader” when their peers are “J readers.”

Quantifiable measurements give students, teachers and administrators the confidence and assurance of “progress”: There is a sense of comfort in advancing from one designated level to the next. But reading is not a science. When we place significant value on quantifiable measures, we also might be pushing readers away from an intrinsic love of reading — and ignoring the great complexity of literature that is simply immeasurable.

This brings us to the reading-level systems themselves. The numbers or letters — which often affect how books are shelved in classrooms, libraries and bookstores — don’t take into account qualitative factors such as vocabulary, story structure, maturity of theme or a child’s developmental readiness.

The Lexile Educator Guide offers a chart of the “typical reader measures by grade” to “connect students with ‘just right’ reading.” Their infographic features a boy carrying books with Lexile levels labeled on the spines. The boy’s quote bubble reads, “My Lexile measure is 1240L. That makes my Lexile range, or reading comprehension ‘sweet spot,’ 1140L to 1290L.” Books outside of his “range” rest by themselves on a library cart.

To demonstrate how the Lexile measure in particular miscalculates books, we took a deep look into its number system. Below, we list the Lexile levels in parentheses for some commonly read books. ( AD stands for adult directed. NC is for nonconforming, meaning they have a Lexile measure markedly higher than the publisher’s intended audience.) Next to each level, we match the book’s Lexile level with the Lexile Educator Guide’s typical grade range:

● “Night,” by Elie Wiesel (590): 3rd grade

● “The Sun Also Rises,” by Ernest Hemingway (610): 3rd grade

● “The Grapes of Wrath,” by John Steinbeck (680): 3rd-4th grade

● “The Power and the Glory,” by Graham Greene (710): 3rd-4th grade

● “Cat’s Cradle,” by Kurt Vonnegut (790): 4th-5th grade

● “The Sound and the Fury,” by William Faulkner (800): 4th-5th grade

● “Extremely Loud and Incredibly Close,” by Jonathan Safran Foer (800): 4th-5th grade

(Harper Perennial)

● “To Kill a Mockingbird,” by Harper Lee (870): 4th-6th grade

● “Invisible Man, by Ralph Ellison (870): 4th-6th grade

● “Fahrenheit 451,” by Ray Bradbury (890): 4th-6th grade

● “Diary of a Wimpy Kid (Book One),” by Jeff Kinney (950 ): 5th-9th grade

● “Tender is the Night,” by F. Scott Fitzgerald (990): 5th-8th grade

● “O is for Orca: A Pacific Northwest Alphabet Book,” by Andrea Helm (1050): 5th-9th grade

(Scholastic)

● “Dear Dumb Diary: Let’s Pretend This Never Happened,” by Jim Benton (1120): 6th-10th grade

● “Aster Aardvark’s Alphabet Adventures,” by Steven Kellogg (AD1400): 10-12th grade

● “Penny Dreadful and the Horrible Hoo-Hah,” by Joanna Nadin (NC1570): above 12th grade

Yes, we selected some dramatic examples. The Common Core says that there are exceptions within reading-level systems, and MetaMetrics has made some adjustments to its numbers in the past couple of years. But we find these exceptions — as exemplified by these titles — to be insurmountable. They demonstrate the fundamental flaw in reducing books to algorithms and creating reading levels based on them.

Children should never be told that they cannot read certain books because they are not in their Lexile level or other comparable measure. We should respect students as readers and act, instead, as facilitators of reading and learning. Kids should read about topics that interest them and pique their curiosities rather than texts that fit within number-crunched factors.

As Teri Lesesne writes in her book “Reading Ladders”: “Reading levels and Lexiles are not the way to determine the rigor of a text. Instead, rigor should be determined by sophistication of thought, depth of character development, stylistic choices, and mastery of language on the part of the author.”

The key to knowing how to teach and challenge our students and children is to read, read, read. This allows us to make recommendations when readers finish books. When we visit stores and libraries, we ask children to select books based on interest. Then, we open the books and read the first pages together. (This can also be done online by opening up the preview pages of books.) Next, we ask the child if the book feels too difficult to the point that it’s very frustrating. If yes, we try another book.

We want to challenge our children, but we also don’t want books to frustrate them to the point that it makes them dislike reading. We trust readers to make that decision for themselves — and with our support, if they need it. If a book is too easy for a child, we should ask ourselves, “Will it be harmful if the child reads the book?” For us, the answer is always no. If we flood children with books of all levels and instill a love of reading, then they will read some books above and below their ascribed reading level. They will be reading with interest, with passion — and with love.

Ricki Ginsberg is an assistant professor of English education at Colorado State University. She formerly taught high school English in Vernon-Rockville, Conn. Kellee Moye is a middle school teacher-librarian in Orlando. Ginsberg and Moye write the blog Unleashing Readers, from which this article is adapted.