The aim of this study is to determine school adaptation problems of primary school students according to teachers' opinions. In this study, embedded mixed method design was used. The sample of this study consists of 909 first grade primary school students and 30 classroom teachers determined by stratified purposeful sampling method. "Adaptation to School Scale" and "semi-structured interview form" were used for data collection. In this study, descriptive statistics and differential analysis were used for quantitative data and descriptive analysis technique was used for qualitative data. As a result of the study, it was determined that 60-65 months old students sometimes experienced adaptation problems, while the students of 66-71 and 72-84 months old almost never experienced adaptation problems. In interviews, teachers stated that as their students' ages decreased, their school adaptation problems increased. Furthermore, school adaptation problems were found to be higher in students who study in Van province and did not receive preschool education. Accordingly, it can be suggested to prepare effective school adaptation curricula for primary school students.