The Advanced Placement (AP) program exposes high school students to college-level materials and then offers an exam each May, which may count for credit or course waiver at colleges. Students earning a 3 on AP exams usually earn college credit, placement, or a waiver of required courses at many colleges. Students should check with prospective colleges as to how AP is credited, since college rules vary. Advanced Placement courses require more homework and are more challenging to students. Students should consider carefully before enrolling in more than one AP class at a time.