I'm at a medium-size college prep school and taught a year-long APCS-AB course. I did most of the algorithms and data structures curriculum in the first semester using Scheme, then moved to Java and the case study in the second semester. My students did quite well on the AP exam and, in my opinion, got much more computer science understanding by this method.
By the way, I had a variety of students in my classes: those with lots of programming background and those with absolutely no experience whatsoever. Both groups did equally well; I credit that to the Scheme work.
Assistant Head of School, Operations and Technology
The Harker School
San Jose, California