In its annual report, the College Board cited two studies that suggest that students who have taken Advanced Placement courses in high school do better in college courses than those who do not, although other recent studies have indicated the opposite.

One of the studies, conducted at the University of Texas at Austin, showed that freshmen who skipped introductory courses because of their AP credits earned higher GPAs and took more classes in the subject in which they received credits than non-AP students.

The students in the study were analyzed through SAT or ACT scores and high school graduation rankings. The other study, which included students from all public higher education institutes in Texas, considered even more measures of success and found similar results.

The studies are the latest addition to a debate over the effectiveness of AP courses. A year ago, research presented to the American Association for the Advancement of Science indicated that AP courses were poor substitutes for college science courses. The study, conducted by Philip M. Sadler of Harvard University and Robert H. Tai of the University of Virginia, sampled 18,000 students at several four-year institutions.

Sadler and Tai found that students who take AP courses did only marginally better than non-AP students. The results showed that students who received a score of three out of five on a science AP exam would earn an average grade of 84 percent in similar course work: Students with honors course work, but who had not taken an AP test, earned an average of 82 percent.

Sadler said that although he supports the AP program and doesn’t want his research to be viewed as “”anti-AP,”” he doesn’t believe the course work is up to the standards of a higher education institution. The College Board questioned the study, citing a nonrepresentative sample group and contrary results from other studies.

Nevertheless, some schools, such as the Massachusetts Institute of Technology, have toyed with the idea of accepting only calculus AP classes for credit.

The University of California currently accepts AP, International Baccalaureate and transferable college courses for credit and, depending on the subject, as equivalent to UC courses.

“”We encourage students to take the strongest curriculum possible,”” Assistant Vice Chancellor of Admissions and Registration Mae W. Brown said.

UCSD offers course-equivalent credit depending on the score and which college the student attends. Brown said that she saw a rise in the number of students applying to UCSD with scores of three or higher on AP tests — consistent with the rise reported by the College Board.

Although incoming students are allowed to use AP credit in lieu of lower-level courses, some feel unprepared for the more rigorous courses.

“”Taking an AP course just means we learn the same material as a college student,”” Earl Warren College freshman Michelle Truong said. “”But it doesn’t mean we go through the same experience. In high school, we were still in our 30-student classes — quite different from the usual 200-plus students in a lecture here.””

Truong said that she feels she should have started at a lower level calculus class than the course her AP credit allowed her to take, but that she was able to get through it regardless.

Truong entered UCSD with credit for lower-division biology, calculus and — from just one AP test — a whole year’s worth of Spanish. Charles Rettig, another Warren freshman, said his AP courses prepared him well for his work in college and that he is comfortable starting off at a higher level.

Brown said that if students are worried about whether AP credit is adequate preparation for their coursework, they should consult their professor and teacher’s assistant.

“”It may require that they think carefully about whether they are prepared to move into the next course,”” Brown said.

The College Board report also ranked states’ AP programs in its report by comparing how many graduating seniors received a score of three or higher on at least one AP exam. California was ranked fifth in the nation at 20.1 percent, compared to the national average of 14.8 percent.

The AP program will continue to expand and add new courses, College Board officials said, including recent additions of Chinese and Japanese AP tests.