If you are choosing a boarding school based on prestige, you are basing your choices on the wrong reasons.If you are choosing a boarding school based upon college matriculation data, you are choosing a boarding school for the wrong reason. If you are asking any such questions without actually having an acceptance to said boarding school, you are way ahead of yourself.
The days of a BS Head of School calling up Harvard and saying “Here is my list of kids I want you to admit” are long gone.
As I have said many many times on this forum, do not go to boarding school if your only purpose is to use it as a stepping stone to a top college; that reasoning is just folly. A boarding school may give a student the tools with which to develop him/herself into a viable candidate, but others schools may as well. Colleges admit students, not boarding schools. While the professionals at the schools are ready and willing to assist in the process, they will not, and should not, do the work for you. Good luck.