We know from previous research that educational achievement in primary, middle school years and at the end of compulsory education is highly heritable. Heritability is a population statistic – it doesn’t tell us anything about a single individual. It describes the extent to which differences between children can be put down to DNA differences, on average, in a particular population at a particular time.
Twins’ exam results
Our new study, published in the journal Proceedings of the National Academy of Sciences, focused on the UK-wide standardised exam results at age 16, the General Certificate of Secondary Education (GCSE). We obtained exam grades from over 13,000 identical and non-identical twins from the Twins Early Development Study who were also assessed on nine broad psychological domains, including intelligence, educational self-belief, personality, behaviour problems, and well-being.
Identical twins share 100% of their genes, whereas non-identical twins, just like any siblings, share on average only half of the genes that vary between people. If overall, identical twins are more alike than non-identical twins on a particular trait, then this implies there is a genetic influence.
Our study showed that the mean results in the GCSE core subjects of English, mathematics and science is more heritable (62 percent) than the nine other psychological domains (35–58 percent) we looked at.
This means that differences in how well children perform at exams are to a large extent explained by the difference in their DNA. Importantly, it does not mean that genetics explain 62 percent of a single child’s school achievement.
Not just intelligence
When we analysed different traits, we found that educational achievement is correlated with many characteristics of children, not just intelligence. Our results indicate that these correlations are largely mediated by genetic factors. To the extent that children’s traits predict educational achievement, they do so largely for genetic reasons.
Although intelligence accounts for more of the heritability of GCSE results than any other single domain, the joint contribution of children’s self-belief, behaviour problems, personality, well-being, and their perceptions of school environment, collectively account for about as much GCSE heritability as intelligence. Together with intelligence, these domains account for 75% of the heritability of GCSE performance.
Indicator of equality
The children in this study were all taught the national curriculum, so to some extent received a similar education. As children’s learning experiences become more similar, they begin to explain the similarities between them rather than the differences between them. As a result of these diminished environmental differences, the relative genetic influences increase. So in a way, high heritability is an indicator of equality.
For example, despite high heritability, with sufficient educational effort, nearly all children could reach minimal levels of literacy and numeracy. This is an explicit goal of education in Finland. Success in achieving that goal would reduce differences in children’s educational achievement, which could change heritability. Hypothetically, if all environmental effects on individual differences (such as educational inequality) were to be minimalised, then the heritability estimate for educational achievement would be 100%.
So what to make of this? Genes are important, not just in educational achievement or intelligence, but in a whole raft of other traits which contribute to how easy and enjoyable children find learning. Education is more than what happens passively to a child. Children are active participants in selecting, modifying, and creating experiences that are matched to their genetic predispositions. In genetics, this is known as “gene-environment correlation”.
At the practical level, our findings add support for the trend in education toward personalised learning rather than a one-size fits all model. None of this means that schools, parents or teachers aren’t important. Of course they are – and each has an important role in helping children achieve the best of their potential.