Washington-area high school students are failing a larger percentage of college course-level exams — losing out on college credit and showing a shortfall in learning — as more of them take the test.

In 2010, 15,439 Fairfax County Public Schools students took 32,230 Advanced Placement exams, with 5 percent more students taking 7.5 percent more exams than in 2009. Participation jumped most dramatically among minority students, with 10.3 percent more blacks and 13.3 percent more Hispanics taking one or more AP exams than in 2009. But only 70 percent of test takers received a passing score of 3 or above, slipping from last year’s 71 percent.