I find it interesting and telling that 1000 Lexile or thereabout is considered anywhere from "high normal" for grade 5 to 10th grade level.

I have a hard time guessing my DD's reading level. I would say she reads like a young adolescent, I guess. Adult-level nonfiction for a literate audience and complex adult fiction (say, Dickens or Austen) are still out of her range and interest. But exact grade level? Who knows.