Black men scored the same as white men in the first test, worse in the second, and still worse in the third. As I recall, black women were not (as) effected.
A new study looked at something similar. They had two groups of women do a math test to "determine whether or not they were capable and smart in math" after getting either supportive or stereotypic messages, and then later they tested them on aggression and self control.
"In these follow-up tests, the women who felt discriminated against ate more than their peers in the control group. They showed more hostility than the control group. And they performed more poorly on tests that measured their cognitive skills," says Inzlicht.This explains so much. Stopping for Haagen-Dazs after a particularly unhappy job interview. Blowing up at the kid. My only caveat would be that I think they tested the people soon after the stereotyping occurred. It doesn't show that it persists, but I believe it does, when such slights continually occur.
This reminds me of Franz Fanon's The Wretched of the Earth, in which he says slaves become lazy and shiftless as a rational response to the condition of slavery.
The lesson for child care and development is not to stereotype kids, but we do with regard to sex, and we probably do with other characteristics, too, such as income and race. State Preschool and Title 5 programs have to be on watch against teachers who stereotype kids based on the fact that mom brings the kid by bus or looks tough, or tattered, or frazzled, or doesn't speak English, or wears a headscarf.