In the present study we examined 1) whether childhood disruptive behaviour, in terms of aggressiveness, hyperactivity and social adjustment, predicts school performance since toddler age or whether becomes it relevant first since middle or late childhood, 2) whether gender differences within the associations between school performance and disruptive behaviour exist, and 3) whether there are trait specific effects in these associations, i.e. whether hyperactivity is more relevant determinant for later school success than aggression and social adjustment. The subjects were derived from a representative, population based cohort study where 3600 subjects we followed for 27 years since their childhood. Our sample consisted of 973 participants (516 girls) who were 3, 6 and 9 years of age at baseline and were followed over their whole compulsory education, i.e. 3 rd , 6 th , and 9 th grades. The most prominent finding was a gender specific association between disruptive behaviour and school performance: hyperactivity predicted later school performance among girls whereas aggression predicted school performance among boys. The association between social adjustment and school performance was less clear. Disruptive behaviour at toddler age (at the age of 3) was not predictable for later school performance but it started to predict school performance at later age, i.e. when it was assessed at the ages of 6 and 9, and the associations were true throughout the whole 9-year comprehensive school. Our findings suggest that early childhood disruptive behaviour has long-lasting effects. Thus, its intervention before the school entry would be of high importance.