I have to chime in here as a reading teacher, as well.
Vocabulary is one of the most complex and intriguing areas of language development, and researchers are just beginning to scratch the surface of what it means to "know" a word. (the huge population of students for whom English is a second language, or who speak a non-standard dialect of English, has driven a lot of the research.)
Some things that apply to this discussion:
1) The single most effective way for children to acquire a rich vocabulary is to read. A lot. Ideally in the company of helpful adults who can quickly explain a word the child doesn't understand. So...if you are writing for young or reluctant readers, you must control your vocabulary, because they lack the experience necessary to access richer text. But if you are writing for more mature or avid readers, it is not a concern. If they don't know the word, they will learn it. From your well-written text.
2) There are many layers of "knowing" a word. A child may have heard the word before, without understanding it. A child may have a vague understanding of how the word is used. A child may be able to explain what the word means. Or a child may be able to give several examples of different ways a word could be used, and explain how that word means something slightly different than its synonyms. (Like explaining why "thin" is a compliment but "skinny" in not.)
So you might use a word that a young reader will more or less understand, using the context of the story, even though that same child couldn't really give a correct definition for it.
3) There is not, so far as I know, an accepted definition of "tenth-grade vocabulary" or "high-school level vocabulary." Word acquisition is so tightly interwoven with personal experience that there simply is no way to make it standard. For example, a friend and I were analyzing a story for second-graders. I knew my Spanish-speaking students would need help with "pond." She said, "Really?" Well, her school HAS a pond next to it. Familiar word.
And kids learn a surprising amount of words form unlikely places. My son was about 5 when he learned "topiary" from some cartoon or another.
4) This point closely relates to the previous 3: When politicians and others talk these days about the "achievement gap," the huge difference in test scores between poor/minority students and the white middle class, they are actually talking about one particular element that affects everything else: Vocabulary.
Study after study has shown that the children of college-educated parents start kindergarten knowing several thousand more words than children raised in poverty. Maybe tens of thousands more words. So on day one of school, when the teacher reads that first story out loud, the middle-class may know and understand every single word, while the raised-in-poverty child only understands one-fifth. Which then affects reading comprehension, which then discourages the child from reading, which means he or she falls farther behind. While that child with the rich vocabulary loves stories, can't wait to learn how to read, reads a lot from an early age, and gets exposed to thousands of new words.
Educators call it "The Matthew Effect," from the Bible quote: The rich get richer, and the poor get poorer.
That last point may not have much to do with the act of writing. But it's an interesting thing to think about, when you're considering who you want your audience to be. Writers like Barbara Park, Andrew Clements and Patricia Reilly Giff are popular with reluctant readers because they know how to tell an engaging story using fairly simple vocabulary and syntax. If that's the audience you're aiming for, then you're asking a very important question.
But as far as I know, there's no list of words or guidelines to follow, except for actual "easy readers." The only way to figure it out, I think, is experience. Studying books you admire, listening to kids speak, tweaking your writing to find the right balance.
Smish
