The College Board’s Advanced Placement program is expanding in American high schools, but as it moves from being a program primarily for elite students, the number of test-takers who fail A.P. exams is growing  although not as much as the number of those who pass.

According to a College Board report, about 800,000 public high school seniors in last May’s graduating class, or 26.5 percent of the class, took an A.P. exam at some point in their high school career, almost twice as many as took A.P. exams in the class of 2001.

While the majority of students who take A.P. exams still earn a passing score of 3, 4 or 5, which is enough to earn college credit at many institutions, the share of failing scores has risen with the program’s rapid expansion. In 2009, about 43 percent of the 2.3 million A.P. exams taken earned a failing grade of 1 or 2, compared with 39 percent of the one million exams taken by the class of 2001.

“Are we getting more 1’s and 2’s? Absolutely,” said Trevor Packer, vice president of the Advanced Placement program. “But are we getting more 3’s, 4’s and 5’s? Even more so. So the question is whether that increase in the percentage of low scores is a reasonable tradeoff for the even larger growth in high scores. And I don’t know an educator who wouldn’t think it’s a good tradeoff to take the risk and give more courses that we know have been good for the few.”