Cultural norms of behaviour influence desirable and problematic behaviours of individuals. In particular, cultural norms should influence individuals’ dishonesty. In a recent Nature study, prevalence of rule violations was introduced as a new country-level measure of behavioural norms. However, information on individuals’ actual honesty was not available due to characteristics of the experimental design. Overcoming this limitation, we show that country-level behavioural norms are related to individual-level knowledge overclaiming behaviour (i.e., claiming to know concepts that do not exist, a measure of individuals’ actual behavioural dishonesty) among 290,954 students from 57 countries (from the 2012 PISA study). Our study represents a crucial test of the argument that cultural norms influence individual's behaviour and of the validity of the measurement of countries’ prevalences of rule violations. These results imply that shaping the behaviour of today's students may result in new behavioural norms that emphasise honesty and rule adherence more strongly.