At a time of mushrooming interest in Advanced Placement (AP) tests, a new book, "AP: A Critical Examination of the Advanced Placement Program," assembles studies on how capable the program is of meeting the increasingly diverse expectations held up for it. Growing out of a symposium held at Harvard in 2007, the book focuses on AP science courses in particular and offers evidence on whether they give students an academic edge in college or persuade them to earn degrees in science-related fields. It examines whether the bonus points that colleges and high schools assign to students' AP grades are warranted, if the program shortens the time it takes to earn a degree, and whether just expanding access to the college-level courses is enough to prepare disadvantaged students for college. Begun in the 1950s to let gifted students undertake college-level work in high school, AP courses have since become "the juggernaut of high school education." Growing at a rate of 9.3 percent a year in the past two decades, enrollment in AP courses well outpaces the 1 percent yearly increase in the number of students graduating from high school, the book says. The interest stems in part from rankings that judge schools' quality based on how many AP courses they offer. Students also increasingly see AP credits as a ticket to college. And education reformers hope that expanding access to AP courses among disadvantaged student groups might help close academic-achievement gaps. President George W. Bush in 2006 also called for training 70,000 more high school teachers to teach AP courses in math and science as part of a broader initiative to boost the numbers of students entering the fields of science, technology, engineering, and math (STEM).