The Chilton parents are very concerned about whether the texts Mr. Medina has chosen will be covered in the Advanced Placement tests.
In the US and Canada, Advanced Placement (AP) is a program which offers college-level curricula and exmainations to high school students. American colleges and universities may grant placement and course credit to those students who get high scores in the AP exams.
Mr. Medina says that the next AP test will be held in the following month (November), but in real life AP Tests are always held in May.
We learn from this that Rory is in the AP English Literature class to improve her chances of attending university. We don’t know what other AP classes she might be doing at Chilton, but any class that she has with Paris seems like a pretty safe bet.