Here are some excerpts from the report:
Assumption #1: The AP program gives students several advantages in terms of college
This section addresses three basic questions: Taking AP classes makes students more likely to succeed in college; AP classes help students get into college; AP programs give students college credit so they can get a degree faster and it will cost less
Studies that simply establish that students who are involved with the AP program in high school perform better in college do not necessarily provide proof that the AP program caused the students to be successful in college. It should come as no surprise that the same motivated, hardworking, and advanced students who take AP classes in high school are still motivated, hardworking, successful students when they get to the university…
… Though somewhat challenging to parse, the research suggests that while AP students, especially those who pass the exams, experience more success in college than do those who did not take AP courses in high school, this success may not be attributable to the AP program alone. Though we found some rigorous studies that after controlling for certain variables showed positive results of the AP program, especially in the sciences, we believe more research needs to be done before we can verify the broad claim that taking AP classes makes students more likely to succeed in college.
…The claim that taking AP courses boosts a student’s chances of college admission needs some qualification: it depends on the college.
Though we know of some cases where students have saved money due to AP credits in college, this tends to be the exception rather than the rule. Research shows that after controlling for background variables between AP and non-AP students, taking AP courses has very little impact on time to degree (Klopfenstein, 2010). In part, this is because colleges treat AP scores differently. For instance, while some colleges allow students to earn college credit with a passing exam score, others may advance students to the next level in a given subject but not award them any credit. … Another reason that the AP experience seldom results in less time to degree is because even among those students eligible to receive college credit, many opt to repeat the course (Sadler & Sonnert, 2010) Finally, it is rare that students pass enough AP exams to skip an entire semester or full year ahead, thus allowing them to graduate in three or three and a half years (Klopfenstein, 2008 & 2010).
Assumption #2: The AP program helps to narrow achievement gaps
…We maintain that using the AP program alone as a tool for narrowing the achievement gap is insufficient. If the AP program is to be used effectively to help make a difference in underserved schools, it will need to be part of a broader initiative that includes changes in professional development and the overall curricular sequence to better prepare students for college-level work.
Assumption #3: AP programs enrich students’ high school experiences
We qualify the claim that the AP program enriches students’ high school experiences: Some students may benefit from an engaging and challenging experience, while others may not. It depends on the teacher, the particular course and curriculum, and it depends on the students and their reasons for taking the courses, their overall workload, and how they handle the increased demands of a college-level class.
While some students might benefit from an AP program, several researchers note some hidden or opportunity costs involved in administering an AP program. Klopfenstein and Thomas (2010) offer three significant ways in which non-AP students at a school may pay the price for the AP program: they may receive lower instructional quality, as the best teachers are siphoned off to teach AP students; they are in larger classes, as AP classes are smaller than typical high school classes; and non-AP course offerings are reduced or limited in order to fund, staff, and expand AP course offerings. In these ways, the presence of the AP program may actually be a detriment to a school. In fact, some teachers and school staff worry so deeply about the negative impact of AP courses and feel so strongly that it thwarts their ability to develop deep thinkers and engaged learners, they’ve dropped their AP program in favor of home grown honors/advanced courses that are not affiliated with AP testing…
Assumption #4: Schools with AP programs are better than schools without AP programs
When implemented thoughtfully and effectively, the AP program may benefit certain students and allow for common assessments across schools and districts. This may be a useful tool for colleges and outside evaluators in assessing school efficacy. However, the presence of an AP program in a high school is not necessarily a valid indicator of a school’s quality…… Students who do well on AP exams tend to do better in college and have higher graduation rates, but it is unclear whether this is a direct result of the AP program. Colleges and universities want the best, the brightest, and the hardest -working students, and enrollment in AP courses may signal this. Yet each institution handles the AP experience differently, and increasingly, universities seem to be moving away from awarding credit for AP courses. Moreover, there are pros and cons involved for high schools that offer an AP program. The program might allow certain students opportunities for higher-level work, yet it also can siphon off the best students and teachers and may reduce the quality of education for non-AP students, and in some cases, cause undue stress for students enrolled in the program.
The report also says:
In the best of circumstances, the AP program can enrich some students’ high school studies and offer opportunities to take challenging college-level courses, with motivated classmates and highly skilled teachers. For certain students who would not otherwise have access to these kinds of college-level courses, the AP program may be particularly beneficial. However, definitive claims about the AP program and its impact on students and schools are difficult to substantiate. Some of the research about the AP program merely establishes correlation and not causation.
The report also gives a series of recommendations for students and schools in regard to the AP program. You can see them here.