Some states have high school starting at 9th grade while some start only in 10th. so when are the kids ready for AP classes? is this school dependent?

Answer 1

Yes, this usually depends on the school and/or district. The majority of students I've heard of who take AP classes start at grade 10, but there's no specific rule that sets a certain age.

Answer 2

I guess it all depends on how smart you are?..