The talk presents the results of two large-scale twin investigations into academic achievement, ability and motivation. The first study investigated the origins of individual differences in numeracy, literacy and general cognitive ability in a sample of 9-12 year old twins. Numeracy and literacy were more heritable than general cognitive ability. Uniform school learning environment may lead to the situation where genetic differences account for most of the observed differences. The second study combined data on academic motivation of 9-12 year old twins from 6 different samples from the UK, Germany, Japan, USA, Canada and Russia. The results showed that family members, even monozygotic twins, were only moderately similar in their academic motivation. These similarities were entirely explained by their genetic similarities. Environmental factors acted to make family members different from each other. These individual-specific environments might include objectively non-shared events and different perceptions of objectively shared environments. These findings provide new insights into complex co-action between genes and environments.