Hey errbody. I own (with two partners) a test prep business in Asia. SAT, APs, stuff like that. Been doing this stuff here since '02, but this is year six of the business.
(my parents are both teachers too, fwiw)
You're right, but I'm dealing specifically with students who are aiming for US colleges and universities--kids who attend international schools (many of which use the IB curriculum, of course), boarding schools in the US (and elsewhere), and the elite Korean foreign language high schools.
Our main business is SAT-1 Writing and CR, but we also do pretty well with AP US History, AP World History, AP English Language & Composition, and AP English Literature & Composition.
Yes, I have a lot of students from US boarding schools (Exeter, PA, SPS, Hotchkiss, etc.). Every boarding school nowadays has a significant Korean contingent, although Chinese students have overtaken Koreans at many schools.