i wouldn't bother, since i write for adults... but if you're new to writing children's stories/books, it's a valuable tool... most work sent me for help that's meant for kids is not written with their vocabulary and reading/comprehension levels in mind, so i usually tell would-be children's authors to check amazon's book listings that include 'stats' and 'concordance' to learn what works best for which age ranges...
Others must have said it already, but a higher score doesn't make your book better. At best, it sells more dictionaries or puts off more readers... Nobody likes pretentious authors.
Quite the contrary, in fact. The reason it is called a readability index is that it was devised to deal with a problem: documents that were so convoluted and complex that they were unclear and unreadable. The lower the score, the more readable the document is. Granted, the problem the index was intended to address was opacity in business and academic documents. And it's probably true that too low a score is also not desirable. After all, you don't want to talk down to your readers. For my part, though, I believe that clear, concise writing is inherently more beautiful. And the index doesn't know anything about the semantics of the document. If you use a short, word that conveys the same idea as three or four longer words, but better, the index will go down. The same thing happens if you substitute a short, common word that fails to do the job that the three or four longer words did. So the index is a purely structural metric. Lowering the index doesn't automatically make the writing better or worse. But simplifying the structure of your writing will make it easier to follow, all else being equal. If you can express the same thought with fewer words, and shorter words, it's a win, especially if the new word choice is more precise. If you separate complex sentences into their component independent clauses, it's also a win. So don't form a complex sentence unless it expresses something that separate sentences do not. Usually, that somnething is a relationship between the clauses that is lost if you separate them. However, that is not the case as often as you might think. The same is true of paragraphs. Like a sentence, a paragraph should express a single idea or event. This is reflected in the index, which favors smaller paragraphs. By itself, the index is only a number. But understanding the rationale behind it can make you a better writer.
In my personal opinion, no computer program can even come close to assessing something such as the readability of your writing. The stories are written for us to read and review, and so it is the human brain that has the most experience in such matters.
