Our country's Advanced placement programs are booming and have been for some time. In May 2000, approximately 769,000 students took 1.3 million AP exams in this country. By May 2009, approximately 1.7 million students took nearly 3 million exams—a growth rate of 130 percent in nine years. The 1990s saw an even greater rate: 145 percent. What's behind this impressive growth?