Alex Tabarrik from Marginal Revolution provides a great example of why economists disagree. I strongly suggest you go to their blog to view the graph and read the rest of the post:
Economix posted a graphshowing a strong positive correlation between SAT score and parental income. Greg Mankiw pointed out that the effect is unlikely to be purely causal because there may be an omitted variable bias, IQ for example. Paul Krugman and Matt Yglesiasboth attack Mankiw and point to graphs showing that income matters for college completion and enrollment, respectively, holding various achievement scores constant. Brad DeLong crunches the numbers on IQ and income correlation to estimate that half the effect is due to IQ and half to something else.
All this is good but none if it gets at the heart of the matter because there are a lot of way that heredity/genes could explain the income/education correlation; IQ is only one possible mechanism, personality (e.g. conscientiousness) is another possibility.
The type of evidence that we need to resolve this question is adoption studies. Fortunately, such studies have been done and indeed I have presented the data before in my post Nature, Nurture and Income. Let’s do so again.
Now what about education? Sacerdote looks at that as well. He doesn’t have a child SAT-score, parent-income correlation but he does find:
Having a college educated mother increases an adoptee’s probability of graduating from college by 7 percentage points, but raises a biological child’s probability of graduating from college by 26 percentage points.
The effect for father’s years of education is even larger; about a ten times larger effect on biological children than on adoptees. Similarly, parent income has a negligible effect, small and not statistically significant, on an adoptee completing college but an 8 times larger and statistically significant effect on a biological child completing college (Table 4, column 3).