Colleges don't see AP scores until after a student is admitted so admissions only sees the fact that the kid is in the class. Also, from what I can tell, admissions offices do have a pretty good feel for the schools they read for.
Once a kid is accepted, schools already give placement tests so that takes care of that issue.
On the credit front, I think partnering with a college would yield better results (like what you did).
I also wonder how much the credits mean - if a kid can knock off a full semester, it's obviously a big saving but given the way colleges charge undergrads - a fixed amount for a varying number of credits, at the end of the day, I wonder if it makes much of a difference for a kid that gets a small handful of credits.