Advanced Placement Music Theory is a class designed for high school students who have completed basic music classes such as band or elementary theory classes. It is a college level class equivalent to the first year theory class in college.
The main course of study revolves mostly around four-part writing à la Bach. It follows all of the rules inherent thereof, such as no steps to a perfect interval, etc. Basically, one starts out learning the basics of this, building up to study of secondary dominants, modulation, and other more advanced topics.
Also covered are modes, basic theory, two-part writing, acoustics, ear training, and composition. Composition is not emphasized, but due to the nature of the course it becomes a large factor later on.
The actual AP exam consists of multiple choice questions regarding ear training and all of the theory learned throughout the course. There is also a free response portion which consists of composition, completing a four-part chorale, and (once again) ear training.
Below are the major topics of the course (to be noded as time permits):
I may upload more as time permits and memory serves...
These all follow eighteenth century rules of harmony, melody, and rhythm, excluding two-part writing, which originates from the seventeenth century.
Sources: collegeboard.com (website), Music in Theory and Practice Volume I (Book) and Volume II (Book)