Results from two countries should be generalized to every country in the world?
If you travelled a little bit like I have, you'll discover a few things.
E.g. The poor are usually uneducated. Meaning they can't help with homework.
Even in poor black American communities, house work is often more important than school work.
More important, the poor tend to work longer and harder on mental jobs.
They most impoverished behave like reptiles (no insult intended) give birth to many children and abandon them to varying degrees. (Fulani people actually, literally abandon their kids and may never see em again)
Read about how American Indian handled children.