They are not “the best” because of or at least not just because of their college placement. There are a group of best schools among public, private day and boarding schools based on objective criteria such as academic offering, extracurricular activities, faculty credentials, student quality, facility, endowment, college placement etc. etc. Meanwhile, there is not one best school for everyone because not everyone needs the same excellence in schools so they can achieve their personal excellence.
My previous post was narrowly address your argument about ivy admit rates vs legacy/athletes.