@Altras The goal of publishing a rankings is always to attract eyeballs that can be monetized (the goal is NOT to provide guidance). If rankings remain the same, people stop paying attention. So publishers have to add and subtract criteria or give the criteria different weights to make sure the lists change. That makes rankings unreliable. Also: Quality of teaching is NOT correlated with test scores or college matriculation…but because it is not easy to measure it isn’t part of the calculation even if it would be at the top of every parent and student list of criteria that matter.
A school that has lousy teachers, but only admits kids with high test scores and/or legacy status at Ivies will end up ranking higher in a list that prioritizes test scores and college matriculation, for example. (Yet no one wants a school with mediocre teachers!) Other hard to measure factors: School culture, stress levels, prevalence of drugs & alcohol, etc…
Boarding school ranking serves an important roll for mindful applicants. Regardless of true value of those highly ranked schools, the rankings will make admission to them very competitive. So compare your list with the ranking. If they are all in the highly ranked list, don’t forget to add enough schools that are not in the top 20.
Unofficial rankings, or the so-called commercial rankings, are written by those in-the-know for those who want to learn more.
Read them as good information but still process and analyze them by yourself.
I think it is safe put to school into groups by its style (academic, artistic, athletic, religious, communal), location (urban, rural, isolated, south, west, east), others (exclusive boarding, mixed, all-boy, all-girl, etc.).
But any way you look at them, some schools have better profiles than the others, but almost all schools have had wonderful students out of their campus.
Such great points, @CaliMex regarding quality of teaching. As a family we are also focused on availability of teachers. We have heard great things from parents and students affiliated with Deerfield, for example, because almost 100% of teachers live on campus, so they are REALLY available to help kids after hours and on weekends. We’ve been told to be mindful of schools where a lower percentage of teachers live on or adjacent to campus.
St. Andrew’s also has almost all faculty on campus, with strategic plan to make/keep it 100%. (also is 100% boarding). It makes a huge difference.
I also agree that having teachers who live on campus is a huge plus since they are available all the time for a quick discussion.
Rankings also ignore culture. One kid’s preppy heaven is another’s conformist nightmare 
So if quality of teaching and your child’s happiness are criteria that matter to you (and they should!) none of these rankings will be useful.