In this NYT Magazine article David Kirp reviews recent studies on IQ heritability, including comparative studies of twins (who are genetically identical) brought up in different environments:
While there is a consensus now that genetic factors play a large role in IQ potential, environmental factors explain a good deal of the variation – and, notably, environmental factors play a very large role for children brought up in poor households. This is a direct refutation of projects like The Bell Curve, which argued that genetic factors are determinative.
Kirp says that this research is support for a universal preschool program. Matt Yglesias takes it in a slightly different direction:
The best way to cope with this would be to take steps to enhance the material living standards of poor adults. That would be a nice favor to the adults and would significantly reduce the challenges facing their children. Unfortunately, while the electorate has a reasonable willingness to try and do things to help out poor kids (because it's "not their fault" that their parents are poor) there's a lot of reluctance to providing serious assistance to poor adults who are deemed to "deserve" their fate. This is a significant political challenge, but I think the policy issue is reasonably clear -- the best way to help poor children is to help poor people generally.