Cambridge (CIE), Advanced Placement (AP) and International Baccalaureate (IB) are all well established programs for high school students to gain college credit through taking high school classes. So what's the difference between them?
AP courses tend to focus heavily on content; learning facts and information and then giving that information back on a test. AP tests are generally focused on multiple choice questions, with a handful of open response questions at the end. In general, even these open response questions focus on providing factual information that conforms with the information provided in the course.
One of advantage of the AP program is that students can select whichever classes they want to take the exam in, so students can engage in a broad range of classes and topics.
The IB program is designed as complete diploma program and focuses heavily on critical thinking and writing. Students follow a more prescribed path through the IB program than AP or Cambridge, with fewer options of courses to choose from. IB tests are primarily open ended response questions designed to demonstrate application of ideas.
The Cambridge curriculum focuses on development and demonstration of critical thinking and writing, as well as application of those skills. Cambridge tests are primarily open ended application questions, including exposure to novel situations students have not encountered before. In addition, Cambridge offers both a program diploma (the AICE Diploma) as well as the ability to selectively take a wide array of courses without participating in the Diploma Program.
Of the 3, the most well known in the United States is the AP. Virtually every college in the country recognizes and accepts AP scores. However, the same is now also true of Cambridge and IB. What sets Cambridge and IB apart is that very few countries outside of the United States recognize or accept AP credit. In contrast, both Cambridge and IB are internationally recognized, and students attending college or university abroad, are frequently able to leverage their Cambridge or IB coursework both for admissions, as well as course credit at international universities.