Good behavior is a necessary condition for effective teaching. There are few children who come to school without problems. Children's behavior at school appears to be strongly affected by within school factors. In this qualitative case study, the teachers' negative behavior with regard to the high school last year students in the classroom setting was defined. The population for this study consisted of 1100 eleventh grade students from three different general state high schools. These schools were selected at random at the beginning of 2007 academic year in Kirsehir, Turkey. The sample consisted of 275 students (male 137 & female 138). The data were collected by means of unstructured interview method. Qualitative content analysis approach was used to analyse data. It was found that "behaving towards the students aggressively" was the most pointed out negative teacher behavior. "Speaking fast" in teaching, "threatening the students with low grades" and "making discrimination among the students" were the more often expressed negative teacher behaviors by the students. (Contains 4 tables.)