Choate has been physics-first since 1980 at least. My physics teacher at Choate, over 35 years ago, went on to be a leading proponent of the physics-first sequence in public schools; he’s mentioned in this article from 2006, wherein he makes the point that the chief obstacle to making physics the core 9th grade science is the difficulty of recruiting qualified teachers who can teach the subject effectively to that age group. https://www.edweek.org/ew/articles/2006/09/06/02physics.h26.html Well-resourced schools like Choate, with decades of experience teaching the sequence this way, don’t have any trouble making it work well.