The Right Age for Learning

Research on the role of age in the processes of learning indicates that, generally speaking, pupils of an older age obtain better scores. This result is explained by arguing that older pupils are more developed from a cognitive point of view. Even limited age differences, such as those within the same classroom, are pronounced at an early age. For instance, eleven months of age difference can account for more than 15% of learning difference at 6 years of age. These effects are said to be diluted along the growth process of the child and disappear in early adolescence.
These studies have yet to delve into the effects of age in the context of higher education. This was the objective of our recent work on Bocconi students (Billari and Pellizzari, 2011, "The younger, the better? Age related differences in academic performance at university", Journal of Population Economics, forthcoming). In our work we find to the contrary that younger students within each group attain better academic results, especially in scientific subjects. We are talking about relatively small effects, on the order of half a percentage point for 11 months of difference, but they are statistically significant.
This finding is not due to a self-selection bias, i.e. the fact than only the most brilliant younger students apply at and get into Bocconi, and it's not due to the fact that the younger ones are those that have early entry into the school system. For example, we have noted that the distribution of the student population according to month of birth is not significantly different from the population at large or the Italian student population.
Why then are the effects of age reversed for university students? Certainly the effects of cognitive growth that favored older pupils at kindergarten and primary school here disappear, but it's hard to conceive that such effect changes its direction. To confirm our findings, we have found that they hold up even after controlling for similar admission test scores, which are proxies of cognitive ability.

Let's thus hypothesize another type of mechanism. Psychological studies have shown that being physically small with respect to one's own reference group at an early age negatively affects the development of leadership or self-confidence. Since we can think that younger students have a set of social interaction abilities that are limited, they might decide to allocate their time between social entertainment and study activities with a preference for the latter. By dedicating more of their lives to studying, they obtain better results. To support this hypothesis, we have analyzed a study on the social and sexual behavior of Italian university students and we find that younger students in each age cohort go less often to the disco, do less sports and have sex less frequently (International Survey of Affectivity and Sex, Max Planck Institute and Università di Padova).
With the idea in mind of reducing difference in academic scores that are directly linked to differences in ability or commitment (something we could maybe define as meritocracy), we can then aim to modify the criteria according to which pre-elementary and elementary school classed are formed, so not to have in the same classroom students having age differences larger than six months (instead of eleven). A solution that would be a zero cost in all schools having at least two classes for each degree of education. This way, the effects induced by the development of social and cognitive skills could be downsized in favor of equal opportunity.