The Flesch-Kincaid reading level is based on an algorithm whose inputs are the number of words, number of syllables and number of sentences. Vocabulary, grammar, idioms and other variables are not considered -- or even if the words make any sense.
Mathew 3:16-17
Lexham English Bible (Grade level 10.8) Now after he was baptized, Jesus immediately went up from the water, and behold, the heavens opened and he saw the Spirit of God descending like a dove coming upon him. And behold, there was a voice from heaven saying, “This is my beloved Son, with whom I am well pleased.”
KJV (Grade level 20.5) And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him: And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
KJV revised (I changed the colons to periods; Grade level 6.5) And Jesus, when he was baptized, went up straightway out of the water. And, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him. And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
Geneva 1599 (Grade level 6.3)
And Jesus when he was baptized, came straight out of the water. And lo, the heavens were opened unto him, and John saw the Spirit of God descending like a dove, and [lighting] upon him.
And lo, a voice came from heaven, saying, This is my beloved Son, in whom I am well pleased.
Holman (Grade level 5.6)
After Jesus was baptized, He went up immediately from the water. The heavens suddenly opened for Him, and He saw the Spirit of God descending like a dove and coming down on Him. And there came a voice from heaven:
This is My beloved Son.
I take delight in Him!
ESV (Grade level 21.3) And when Jesus was baptized, immediately he went up from the water, and behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him; and behold, a voice from heaven said, “This is my beloved Son, with whom I am well pleased.”
ESV revised (I changed a semicolon to a period; Grade level 10.6) And when Jesus was baptized, immediately he went up from the water, and behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him. And behold, a voice from heaven said, “This is my beloved Son, with whom I am well pleased.”
ESV revised again (I changed some commas to periods; Grade level 7) And when Jesus was baptized, immediately he went up from the water. And behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him. And behold, a voice from heaven said, “This is my beloved Son, with whom I am well pleased.”
The pledge of allegiance, BTW, is at Grade Level 15.2. And Jabberwocky comes in at 3.2.
Make of it what you will.