Hi Luvflorida,
I haven't heard of anyone taking the AP English exam in grade 9, which is not to say that it isn't done, but I would think it's quite rare. My high school set it up such that the bright freshman took the "easier" APs, the ones that only required one year of prep, in 9th/10th grade (think human geography, environmental science, statistics, European history, biology) and the "harder" APs, the ones where you need to spend significant time in preparation, in 11th/12th grade (think Calculus BC, Physics C, Chemistry, English Language, CS AB, Latin). I took the AP English exam in 11th grade, and Philosophy in 12th grade.
I could see a district placing a 9th grader in an AP English exam only under circumstances where they think the kid will graduate early. There's a major advantage to having the kid hold off ... if they're that bright, they should spend a couple of years preparing and get a higher score.
DC