A higher percentage of students in public high schools are taking and passing Advanced Placement exams, according to a report issued Wednesday by the College Board. The gap between the performance of black and white students, however, remains large.

Advanced Placement courses, which offer college-level study in 37 subjects, are prepared by the College Board and have been widely seized on as a good route to increasing the rigor of a high school education. The exams are scored on a five-point scale, and some colleges offer course credit to students who pass, earning a score of 3 or above.

The proportion of students taking the courses has grown slowly but steadily over the last five years, as has the percentage of students with a score of 3 or higher.

Last year, more than 15 percent of the 2.8 million students who graduated from public high schools scored a 3 or above on at least one A.P. exam. In 2002, 11.7 percent of the graduates got a 3 or better on at least one exam, as did 14.7 percent of the 2006 graduates.