Flesch–Kincaid grade level
Flesch–Kincaid Grade Level converts average sentence length and syllables per word into an approximate U.S. school grade. A score near 8 means “around eighth-grade reading,” not a quality score.
It pairs with Flesch Reading Ease: easier text usually shows a higher ease score and a lower grade. ClarityScore shows both so you can revise with two views of the same draft.