There are over 34,500 private schools in the US, and Pollyanna is covering 60 - admittedly, 60 with an outsized voice on the right tail, and so it's probably a litmus test of where the broad market is going. So to mithawk's point, the antiracism policies might not be a differentiator within-category, but are becoming table stakes to reinforce perceived value differences between categories. At least, I suspect that's the thinking of the administrators.
Re: groupthink? My personal opinion is this is CYA tokenism on the administrators' parts. I doubt these administrators actually believe what they're instituting, at least not to the degree that dissenting parents are characterizing the programming, but are aware of:
a) How divergent their demographics are from the mainstream - and, by extension, how it might look for prospective donors to make endowments with institutions that are less than sterling reputation-wise
b) How public opinion is increasingly turning to the intersection of affluence and racism
c) Their next jobs will require proven EDI programming
Several giants have fallen in the public sphere to allegations of racism in the last year, and these policies are (IMO) insurance as the larger world shakes out its take on racism, and the appropriate balance of institutional responsibility to redress it.
As I've said upthread, perhaps I'm being cynical. But to see such wild swings in curriculum ideology suggests the views were not held innately before, particularly where actual interaction with under-privileged and marginalized communities is slim to nil.
