I read an article many years ago that said the biggest indicator, the thing with the strongest correlation to educational success in terms of test scores and graduation rate was ...
"Number of Hours a day that an adult living in the Home with the child spend with them on educational work, such as homework"

now ... take that thought, and extrapolate to very broad cultural norms in our country....

which cultures tend to have single parents, who are working one or two jobs just to put food on the table.... and how do those kids usually do?

which cultures tend to have multiple generations living together, who might have as many as 4 or 6 adults in the household who can spend time with the children and work on homework ... and how do those kids usually do?

it's honestly all about time ... and who has the time (or makes the time) and who doesn't