Violence can be defined as the intentional use of physical force or power, threatened or actual against oneself, another person, or against a group or community, that either results in or has a high likelihood of resulting in injury, death, psychological harm, mal development or deprivation [1]. In this context, violence in school can take the following forms, from mental, or psychological, to physical violence: assault - physical or sexual, bullying, drug trafficking and related violence, gangsterism, hazing or initiation, intimidation, murder, racially motivated violence, rape, robberies, sexual harassment, shootings, stabbings, theft of property and vandalism. The purpose of the present study is to identify the degree to which various factors, such as irrational and rational assessment cognitions, automatic dysfunctional and irrational thoughts, emotional growth, respectively, are associated with aggressive behaviour in high school students. The study also tracks possible gender differences in terms of the above-mentioned factors (irrational and rational assessment cognitions, automatic dysfunctional and irrational thoughts, emotional growth) in teenagers. The study participants, aged 16 to 19, attend high school classes in Timisoara.