We investigate the impact of the school-starting-age on cognitive and non-cognitive skills of
boys and girls between the ages of 6 and 12. Using Australian data, we are able to distinguish
schools-starting-age effects from age-at-test effects. Results point to large and significant
gender differences in school-starting-age effects. In particular, boys starting school younger
show more behavioural problems (esp. hyperactivity) and have lower academic achievement
in reading and numeracy. In contrast, girls do as well whether they start earlier or later.
Teachers appear to be underestimating younger boys' behavioural difficulties which may
contribute to the persistence in the effect of school-starting-age effect on boys' academic
achievement between 6 and 12 years old.