A very interesting set of results on the effect of family income and ethnicity on SAT scores in the US [Hat tip to Droolrag for the pointer]:
... [We] looked at the College Board’s 2009 California demographic research study and parsed out the data showing scores by income and ethnicity, and then added an aggregate mean for additional review. This data shows that test-takers with family incomes of less than $20,000 a year had a mean score of 1310 while test-takers with family incomes of over $200,000 had a mean score of 1715, a difference of 405 points. Further calculations showed a 40-point average score increase for every additional $20,000 in income.
A look at the details reveals that the income advantage is even higher at the low end: For income under $100,000, the advantage is nearly 60 points for every additional $20,000 in income.