When processing information about their world, people systematically reduce objective complexity. This is true not only of cognitive problem-solving, but also other everyday situations, for example where decisions are required in situations relevant to morality. The developmental psychological perspective suggests that the adequate handling of situations like these requires, on the one hand, an age-related, increasing differentiation in social cognition and, on the other hand, an ever more effective structuring and integration of information. However, the operation of the latter developmental process might carry the risk that complexity reduction (in the sense of oversimplification) substitutes for adequate psychosocial development. Undue emphasis on complexity reduction may suggest situation-specific action alternatives, which though inappropriate, are 'easier to handle'. In an empirical study using 176 pupils from Polytechnic High Schools in (East) Berlin, we test the hypothesis that a tendency towards oversimplification in (fictitious) situations of moral relevance is systematically related to deviant behaviour at school. Results show that students exhibiting deviant behaviour do indeed have a stronger tendency to oversimplify social cognition. It can also be shown that the frequency of complex social cognitions generally increases with age. This trend, however, is found for non-deviant students only. For deviant students a decrease in complex social cognitions with increasing age was found. Furthermore, it can be shown that these results are not confounded with the effects of gender or academic grade.