A very large genetic study has revealed that genetic differences have little effect on educational achievement. The study involved more than 125,000 people from the U.S., Australia, and 13 western European countries.

All told, genes explained about 2% of differences in educational attainment (as measured by years of schooling and college graduation), with the genetic variants with the strongest effects each explaining only 0.02% (in comparison, the gene variant with the largest effect on human height accounts for about 0.4%).

http://www.futurity.org/society-culture/genes-have-small-effect-on-length-of-education/

[3443] Rietveld, C. A., Medland S. E., Derringer J., Yang J., Esko T., Martin N. W., et al.
(2013).  GWAS of 126,559 Individuals Identifies Genetic Variants Associated with Educational Attainment.
Science.