This study was conducted to determine teachers’ level of information about the principles of preparing tests and teachers’ level of awareness about violated principles in the different booklets prepared for each candidate by OSYM. This research was carried out with case study as one type of qualitative research. 15 high school teachers teaching in different branches participated in this study. When teachers, as participants, were being determined, the maximum diversity sampling method, among purposive sampling methods, was used. The data of the study were obtained by using “Teacher Interview Form” which was prepared by the researchers. The interview form was designed after having been analyzed by an expert, and a pre-evaluation process with three teachers. For the data analysis, both descriptive analysis and content analysis method were utilized. Research results showed that the teachers who participated to this study don’t have enough information about the principles of preparing tests and are not sufficiently aware of the principles that have been violated in different booklets prepared to the use of each candidate by OSYM. The teachers who are aware of the principles that have been violated in the process of preparing these booklets stated that reducing the number of booklets would be more suitable application instead of applying different booklets for each candidate.