<p>There are three separate issues here: getting admitted; getting credit and getting placement into more advanced courses.</p>
<p>For admission, colleges look for the most rigorous course load available to the student and to evidence that the student has done well in the courses. APs and IBs certainly are evidence of a rigorous course load (though colleges take into account that many schools do not have either APs or an IB program, or that they offer only a limited number of APs). Taking college courses is another evidence of a rigorous course load. This can be done at the local college or through distance learning programs such as EPGY.</p>
<p>Getting credit: With a sufficient number of credits, a student may earn Advanced Standing, allowing that student to graduate one year early. This policy is observed at a number of schools. There are many that do not allow students to earn Advanced Standing, no matter how many APs or IBs that student came with.
Each school has its own policy for awarding credit. Some APs count, others do not; some count for full credit (one year), others for only half (one semester). I have actually found that Harvard is more generous than many other top schools in this regard. One need only four APs to obtain Advanced Standing, and there is no stipulation as to distribution across fields (as there is for Princeton, for example). However, note that only some APs will earn credit; and for Harvard, only scores of 5s on APs and scores of 7 on IBs will count. At other top schools, scores of 4 on certain exams are acceptable.
College courses taken elsewhere do not count toward Advanced Standing (not even Harvard Extension courses!). </p>
<p>Placement: At Harvard and elsewhere, even when no credit is awarded for APs, IBs or college courses, a student may be allowed to take more advanced classes. This can be done by looking at the course description or by a placement test. </p>
<p>It has been found that about 30% of students matriculating at Harvard have enough AP/IB credits to obtain Advanced Standing but that only about 24% avail themselves of the option. The rest prefer to use their scores to place in more advanced classes but stay the full four years. </p>
<p>Hope this helps.</p>