Note: this is the second of two three companion posts to Episode 44 of my podcast, Children’s Science Fiction. (I told you, this episode took a lot of research.) For the first post, click here.

Today, children’s books—especially fiction books—are grouped into different markets based on age—chapter books, middle grade, upper middle grade, and so forth. On its face, that sounds sensible, because a fifth-grader is going to be able to read more complex texts than a first grader and will be able to handle a wider range of subject matters. The thing is, this didn’t used to be the case. Little more than a half century ago, you didn’t see those divisions. Instead, there were others; picture books were still distinct, but there were “boys’ books” and “girls’ books” with rather sharper lines between them than we have now. The age-based markets weren’t really a thing.

This was one of the surprising things I learned while researching my upcoming podcast episode on children’s science fiction. Reading level seems like a natural way to divide up books, but that entire paradigm is a fairly new one. It grew up out of the shifts in the children’s book industry in the 80s and 90s. (Or at least, it grew up alongside them. I don’t have direct evidence, here.) During this time, children’s fiction was pushed more in school through the Scholastic Book Fairs, and for schools, children’s publishers (not just Scholastic, but also others like Harper-Collins) began breaking books down by grade level—or rather, by reading level.

(Actually, in my personal experience, I feel like the release of the Accelerated Reader program in 1998 may have had an even bigger effect in spreading the “reading level” paradigm, but that was after the overall market had realigned itself.)

Reading level, or readability, is just what it sounds like: a measure of the complexity of a book in terms of what level of text children are expected to be able to read at a certain grade level. In principle, reading levels are not new. Using grade-by-grade primers to teach reading are an old idea…but even then, not exactly as they are today. The famous McGuffey Readers from 1836 were spaced out at two grade levels per book. Zeroing in on individual grade levels or even narrower was a newer idea, and the mathematical approach to recreational reading is even more so.

There are loads of different readability metrics, usually based on some mathematical formula involving sentence length, word length, vocabulary size, and the like. Whatever system you use, the main point is that it allows a catalog of books to be broken down by grade level—or even fractions of a grade level. (Scholastic’s own Guided Reading Level uses an A-Z system to cover grades K-6 to dial in to a quarter of a grade level.) The goal is to recommend books to kids that are just challenging enough to improve their reading skills. At least that’s the theory; many people dispute whether reading levels are helpful or even accurate.

Regardless, the paradigm has become so pervasive that the children’s fiction market—as seen in actual bookstores rather than school libraries—is divided by age in a suspiciously similar way. And that’s before the internet; Amazon lets you search by individual grades if you want, but the way books are marketed isn’t quite that granular (yet).

Most of the children’s lit markets form overlapping age ranges four years wide and two years apart. This isn’t exact, and you’ll often see different numbers, but they’re usually around this breakdown:

• Picture books are self-explanatory. They’re an older category less rigidly defined by age, but you’ll frequently see them listed as ages 4-8.
• Chapter books are usually meant to mean kids’ first chapter books after they grow our of picture books. They’re usually listed as ages 6-10.
• Middle grade is what we normally think of as “children’s books”—the Narnias and Roald Dahls of the world. “Middle grade” here doesn’t mean “middle school,” but rather “middle grade school,” perhaps in the old K-8 sense, thus ages 8-12.
• Upper middle grade is the most nebulous category. It was created to fill in the gap between middle grade and young adult at ages 10-14, but there’s a lot of overlap.
• Finally, young adult (YA) fiction is marketed to teens, or if we’re following the pattern more closely, ages 12-18.

That’s how the market breaks down, but where did these terms come from?

The earliest (besides picture books) and probably clearest case is young adult fiction. YA as we know it today is generally considered to have begun with S. E. Hinton’s The Outsiders in 1967. It’s worth noting that historian Farah Mendelsohn also noted a distinctive shift in children’s sci-fi associated with this paradigm around 1970. Before this, the market was more about “boys’ books” and “girls’ books” (see Heinlein’s juveniles, for example), and was more nebulous in terms of age. For example, Madeleine L’Engle struggled to get A Wrinkle in Time published in 1962 because, as a sci-fi novel with a teenage girl protagonist, it crossed the usual boundaries and didn’t have a clear audience. Now, of course, it’s one of the classics—maybe even the classic of children’s sci-fi.

So, this gives us YA, picture books, and the original “children’s books” in the middle. How did that middle category formally become middle grade? That one I’m not as sure about. I didn’t know what to search for that wasn’t too generic to be useful, but I thought Google Books Ngrams might be good for a quick look. Based on those results, searching for things like “middle grade” and “middle grade fiction,” the idea of a distinct market named as such seems to be a product of the 90s. The term is much less used before then compared with “children’s books.”

Ngrams also helps pin down chapter books. The use of the phrase “chapter books” for kids’ first and easiest books with chapters dates back to the 80s, and in that case, that usage was specifically driven by children’s publishers like Scholastic and Harper Collins. The New York Times Best Seller List instead defines “chapter books” as ages 6-12, including middle grade.

I don’t know where the term “upper middle grade” came from. It’s too little-used to get a clear picture of it from Ngrams or Google Trends, and simple web searches don’t turn up anything definite. However, it’s widely regarded as a new or emerging market, only recently divided from traditional middle grade, so it’s probably the newest term, at least in widespread use.

The point is that these are all fairly new classifications—certainly much newer than children’s lit in general, which dates back at least to the 1800s, and yet today, they are indispensable for writers, who need to know their audience and be sure of what age group they’re writing for. It’s been a complete overturning of the paradigm before 1967 and has fundamentally changed the way we think about children’s literature.

However, there is one big caveat to all of this, which is that what market a book falls in is just that—marketing. It’s a rule of thumb based on what publishers think kids will be interested in and the complexity of the language. They already overlap, and the lines have only become blurrier since the 90s, as Harry Potter proved that plenty of kids have no problem reading 800-page, nominally YA books. And what’s more, publishers have an incentive to market their books broadly. I’ll talk more about that in the next post.