From Diverse:

White children who attend schools with little ethnic diversity are more likely to blame a Black child than a White child when they are asked to identify the source of potential misbehavior, concludes a new study.

“The effect of school composition matters,” Killen says. “In homogenous schools, children have very little contact with people of other races … and this can create an ingroup bias.”

She says that although young children are not aware of historical patterns of exclusion, they pick up subtle messages from adults and see it in a larger context.