I think this is an isolated incident where the worst thing the principal was guilty of is shortsightedness. Especially since black women are not traditionally know as oppressors, as a matter of fact, black women might be the MOST oppressed demographic in the last 500 years.
I think it's more "woke" to try to turn this into segregation than the principals actions. Like I said, it was poorly thought out and short sighted. She probably reasoned it by saying "different kids learn differently, so let's try this" similar to how we may have private all boys or all girls schools.
This incident, in my opinion, is no more racist than an all girls Christian/catholic school is sexist