What they found was that most of the candidates used grammar typical of students in grades 6 to 8. Trump's grammar fell just below 6th grade, but not as low as former president George W. Bush's, at around 5th grade. Rubio, who has suspended his campaign since the study began, was the highest of this year's candidates, about a half-grade above Cruz, Clinton and Sanders. (John Kasich was not included in the analysis.)