I like the Bernie/Biden analogy!
I think that bs’s generally lean liberal, California ones just do it with a California vibe. The social justice warrior (for lack of a better term, I don’t mean it as a pejorative) is probably no more of a thing in a California boarding school than a typical East Coast bs. A sjw can find a good number of like-minded folks at any of ‘em. If anything, my impression is that conservatives are in the significant minority at almost all boarding schools.
Are you asking about political leanings of the student body or approach to teaching? If it approach to teaching, what are you looking for? Living on a working farm, alternative curriculum, very artsy, very environmentally focused, different grading system? Political extracurriculars?