... As I alluded to with the "(or guardians)". Genes have no major correlation. I'm sure there are obvious exceptions with learning disabilities etc. If a higher class family adopted a lower class child, the childs academic achievement would improve.

Conversely if you have super intelligent biological parents... but are raised in a low-socio and low-education level family... your academic results are poor.

In summary: Genes have nothing to do with it.

If you are actually interested in good education policy you should read:

http://en.wikipedia.org/wiki/Ernest_R._House