When you think about a sentence, you usually think about words — not lines. But sentence diagramming brings geometry into grammar.

If you weren't taught to diagram a sentence, this might sound a little zany. But the practice has a long — and controversial — history in U.S. schools.

And while it was once commonplace, many people today don't even know what it is.

So let's start with the basics.

"It's a fairly simple idea," says Kitty Burns Florey, the author of Sister Bernadette's Barking Dog: The Quirky History and Lost Art of Diagramming Sentences. "I like to call it a picture of language. It really does draw a picture of what language looks like."

I asked her to show me, and for an example she used the first sentence she recalls diagramming: "The dog barked."

"By drawing a line and writing 'dog' on the left side of the line and 'barked' on the right side of the line and separating them with a little vertical line, we could see that 'dog' was the subject of the sentence and 'barked' was the predicate or the verb," she explains. "When you diagram a sentence, those things are always in that relation to each other. It always makes the same kind of picture. And supposedly, it makes it easier for kids who are learning to write, learning to use correct English."

An Education 'Phenomenon'

Burns Florey and other experts trace the origin of diagramming sentences back to 1877 and two professors at Brooklyn Polytechnic Institute. In their book, Higher Lessons in English, Alonzo Reed and Brainerd Kellogg made the case that students would learn better how to structure sentences if they could see them drawn as graphic structures.

After Reed and Kellogg published their book, the practice of diagramming sentences had something of a Golden Age in American schools.

"It was a purely American phenomenon," Burns Florey says. "It was invented in Brooklyn, it swept across this country like crazy and became really popular for 50 or 60 years and then began to die away."

By the 1960s, new research dumped criticism on the practice.

"Diagramming sentences ... teaches nothing beyond the ability to diagram," declared the 1960 Encyclopedia of Educational Research.

In 1985, the National Council of Teachers of English declared that "repetitive grammar drills and exercises" — like diagramming sentences — are "a deterrent to the improvement of students' speaking and writing."

Nevertheless, diagramming sentences is still taught — you can find it in textbooks and see it in lesson plans. My question is, why?

Burns Florey says it might still be a good tool for some students. "When you're learning to write well, it helps to understand what the sentence is doing and why it's doing it and how you can improve it."

But does it deserve a place in English class today? (The Common Core doesn't mention it.)

"There are two kinds of people in this world — the ones who loved diagramming, and the ones who hated it," Burns Florey says.

She's in the first camp. But she understands why, for some students, it never clicks.

"It's like a middle man. You've got a sentence that you're trying to write, so you have to learn to structure that, but also you have to learn to put it on these lines and angles and master that, on top of everything else."

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