TL;DR: In the study, a number of White and Black children were adopted into upper middle class homes in Minnesota, and the researchers had the adopted children take IQ tests at age 7 and age 17. What they found is that the Black children consistently scored lower on IQ tests, even when controlling for education and upbringing. Basically the study suggests that IQ is to an extent genetic, and the population genetics of different ethnic groups are a contributing factor to differences in average IQ and achievement.
TL;DR: In the study, a number of White and Black children were adopted into upper middle class homes in Minnesota, and the researchers had the adopted children take IQ tests at age 7 and age 17. What they found is that the Black children consistently scored lower on IQ tests, even when controlling for education and upbringing. Basically the study suggests that IQ is to an extent genetic, and the population genetics of different ethnic groups are a contributing factor to differences in average IQ and achievement.