Nowadays, we can increasingly face aggression in preschool children. Aggressiveness can be defined as socially unacceptable behaviour intended to harm another person or object. By species, we can divide aggressiveness into physical and verbal, and by causes of appearance into unintentional and intentional aggression. The causes of aggression can be biological, social, mental, and as one of the most frequent factors we could mention the influence of the media, which is increasingly present today. Gender differences in aggression are the consequence of differences in the socialisation and upbringing of girls and boys that are mostly influenced by parents. When we talk about aggressiveness in kindergarten, we mean fighting, seagulls, swearing, insulting, provocations, kicks, bites, sticking, hair withdrawal, toy abduction and destruction, mockery, tampering and confusing. The prevention of aggressive behaviour can be divided into primary, secondary and tertiary aid. One of the most important in preventing children's aggressive behaviour is the partnership between family, kindergarten and school. Partnership is usually explained as a process in which individuals or institutions involved endeavour to support each other, harmonise their efforts and contributions with a view to positive outcomes in the future, in this case a healthy development of children.