Comment by hagbard_c

Yes, there does seem to be a genetic component to IQ but as I stated you don't need to include it here to explain why cultures which place emphasis on education and discipline score higher than those which don't. Even if intelligence were not heritable those cultures would on average still perform better than those which don't value education and discipline. Adding a heritable component makes the effect stronger, especially in cultures where intracultural marriages are common or the norm.