<p>"my S cannot use his Harvard Extension courses for credit at Harvard! But he can use his AP credits to get Advanced Standing."</p>
<p>This is exactly the reason to take APs and not college classes. My kids also took some classes at a well-respected "top ten" university, and did not get credit for those at their respective colleges (Stanford and Swarthmore), but they did get lots of credits for APs. All colleges have very straightforward policies regarding AP credit, with list of exams and grades needed. Situation is very murky with credit for college classes (and for good reason, as quality varies widely, whereas AP tests are all the same). College classes are also much more expensive, especially if taken at private uni.</p>