See Baby Discriminate
Kids as young as 6 months judge others based on skin color. What's a parent to do?
It's by San Francisco novelist Po Bronson and his wife Ashley Merryman, both terminally SWPL. It's a chapter from their self-help book Nurture Shock, and it explains how to more scientifically indoctrinate your children in the conventional wisdom so they don't slip up and inadvertently say something politically incorrect about race, thus exposing them, and you, to who knows what consequences.
I'm sure parents in Stalin's Soviet Union had similar worries. Bronson and Merryman would no doubt have done land office business peddling advice to kulak parents about how to talk about class so their little ones don't slip up.