It's a limerick ...Not original.
Not that atypical for a ten year old ... I wouldn't worry that much ... If the child were mine I wouldn't do more than a mild chastisement for being crude and not that creative.
If he is a ten year old in the third grade, one must limit one's expectations. In any event, I doubt that he wrote it himself.
If I recall correctly, ten year olds are like that. Most of them haven't yet reached puberty, but they are starting to become aware of sexuality.
Well, it rhymes :) Sorry, laughing at the mental picture. If that happened, it truly is sad.