The purpose of this study is to determine undesirable behaviours of primary school students, to define the factors leading to these behaviours and to detect the methods applied by teachers for changing these undesirable behaviours. The data of this research were obtained through a survey comprised of two sections developed by the researcher. This survey including three open-ended questions was applied to 355 teachers and the data gathered were assessed using descriptive analysis method. Undesirable student behaviours that teachers encounter in the classroom seem to be talking without asking permission for it, walking around in the classroom without permission, continuously complaining about friends, not acting responsibly in compliance with group activities, talking disrespectfully to the teacher, acting pretending to be the characters in TV series, jealousy in relationship with friends, and having attention deficit. Teachers consider that the reasons for these undesirable behaviours are the fact that parents interfere in education-teaching process, extremely spoil their children, compare their children with their peers, force them to participate in various courses, act as if they were teachers in their relationships with teachers and that there are not adequate playgrounds in school yards, there is vulnerability of safety in schools, there are not adequate fields for activities of sports in schools. It is observed that the primary school teachers who participated in the research use for changing these undesirable behaviours the method of reminding classroom rules, calling the student's name, giving advice, encouraging for apologising, warning trough eye contact, changing seats of students, complaining about the student to his/her parents, prohibiting students from having a break, retracing to the source of the problem, visiting the student at home, discussing the problem with the school counselor and ignoring the behaviour.