Actually it seems the boarding school wich supplies most Ivy League students is in Singapore, from some research I did earlier. My elder kid, keen on joining a boarding school, is afraid of Singaporean discipline though, besides probably beeing not eligible. On the other hand she'd pack up for Switzerland instantly if we offered her the oportunity.
I'm also a fan of Switzerland but will definetely look more into UK boarding schools if we decide to send them to boarding school, if they are as good but considerably cheaper I wouldn't mind (9 of the 10 most expensive high schools in the world are in Switzerland from memory, they make asian international schools look like pauper hang outs tuitionwise)
Anyway my beef, like Marketsurfer's, is many international and prep schools seem to be geared towards forming Art majors - striking here with lavish Art and Music classrooms but blah science rooms as well as maths teachers with a suspicious background, at least in middle school.
Luckily here a new american school opened recently, which boasts great academic results in other parts of the world, so the more established schools need to pick up. Great results last year at IB, and kids got into good name colleges, but I wonder how many of them are stem majors (actually waiting for some feedback from the principal and will start a related thread).