I thought about it for some time, and the study is absolute rubbish -- Wikipedia really should not link to such a sketchy study. The problem with this study and similar studies is:
1. They try to show some kind of weak correlation between two variables without varying all other variables sufficiently. I found inconsistencies, faulty experimentation, and implicit caveats in similar studies, with the conclusion that IQ is not _correlated_ to anything -- humans are not FLOPS-rated CPUs, and the studies are highly misanthropic.
2. The studies don't have anything actionable, and serve no purpose other than to reinforce eugenics views.
Something like "The effect of early intervention in African American children" is a much more credible study, with a clear control group, and clear actionable items.
This Wikipedia page is highly problematic, making wild speculations, citing sketchy old studies and missing citations for many things: https://en.wikipedia.org/wiki/Intelligence_and_education -- please fix it if you're able. I marked it as a hoax for now.