2prepmom means this site http://www.boardingschoolreview.com/
All these schools admit less than 15% of applicants. For international students, especially for Hong Kong, China, S. Korea where hundreds of students from each country apply to each school, the acceptance rate can be as low as 5%.
Here is a useful read but for an American student –
http://talk.collegeconfidential.com/prep-school-parents/1174214-one-family%C2%92s-bs-search-and-application-process-%C2%97-start-to-finish-p1.html
Never to early to consider “casting wider net,” that is to consider less selective, wonderful schools –
http://talk.collegeconfidential.com/discussion/comment/12527527/#Comment_12527527
http://talk.collegeconfidential.com/prep-school-admissions/1687542-identifying-hidden-gem-schools-by-the-numbers-and-considerations-for-admissions-after-9th-grade.html
The Admissions Officers travel all over the world to market their schools. Look for Boarding School Fairs in your area and attend it to learn more about application process and talk to past students.