The private school my children attend now is about 50/50 black and white. The difference is the children know that the school will not tolerate any form of discrimination. It has actually turned out to be a pretty good thing becuse my children have learned that not all black children have been raised by their parents to hate whites.
Sounds like you made a good choice for your children.
My middle son left his private racially-mixed high school at the beginning of 12th grade to go to the local public school because he thought he was missing out on something.
He (over 6ft at the time) was bullied by black GIRLS! They would call him names and physically pushed him. He left the public school within a week to go back to private school.