More students than ever are achieving high scores on Advanced Placement examinations, according to data released by the College Board Wednesday. But the report also noted continuing gaps among racial and ethnic groups -- with minimal progress for black students.

For the high school class of 2008, 15.2 percent of students scored a 3 or higher on at least one AP course while in high school. A score of 3 generally suggests a good understanding of the material and tends to be the minimum level at which some colleges will award credit for the work. That percentage is up from 14.4 percent for the previous class, and from 12.2 for the class five years prior.

AP courses have grown in popularity over the last decade, with many students seeing them as a way to impress college admissions officers. While there is much debate over whether the courses really represent college-level work, even many educators who are skeptical of AP meeting that standard praise the programs for adding rigor and keeping students engaged in the senior year of high school.

As AP has become a key way for top high school students to demonstrate their academic abilities to colleges, concern has grown over the participation gaps among different demographic groups. Wealthier high schools tend to offer many more AP courses, while high schools in low-income areas with many minority students tend to offer far fewer AP options. The College Board has made a major push to expand both participation and success rates on the exams, providing grants and support to high schools that serve low-income students and are working to expand AP.

The data released by the College Board on Wednesday show some progress -- for some groups that have not historically achieved high levels of participation. For example, 17.0 percent of AP test-takers in from the class of 2008 were from low-income families, up from 16.2 percent the previous year. And these low-income students made up 13.4 of students achieving at least one score of 3, up from 13.1 percent the year before.

The College Board has set a goal of closing the "equity and excellence gap" for all states -- a goal that is achieved when the percentage of students from various groups achieving at least one score of 3 equals their share of the state population. As of this year, 18 states have closed the gap for Latino students and 16 states have done so for Native American students. No state has closed the gap for black students.

Nationally, the percentage of public high school students who took at least one AP exam (regardless of score) shows the extent of the gaps. For white and Latino students, the proportions of those in the total population and the AP population are similar. Asian students are much more likely to take an AP exam and black students are much less likely to do so.

High School and AP Test-Taking Populations by Race and Ethnicity, Class of 2008