This research was conducted to evaluate the efforts made by Turkish teachers on developing written expression in their classrooms by considering the basic principles of the process-based writing approach and to determine whether the students' written expressions meet the basic principles of the process-based writing approach. In this respect, the method of the research was determined as a case study, a qualitative research design, and the study group consisted of 24 Turkish teachers teaching 5th, 6th, 7th and 8th grades and 24 students enrolled in these classrooms. Maximum variation sampling, a purposeful sampling method, was used to form the study group. A semi-structured interview form was used with 24 selected teachers, and the practices of these teachers and the reactions of the students in these classes were observed. A content analysis was completed in analyzing the data obtained from the observation and interview forms. In addition, the texts written by the students participating in the study were analyzed using the planned writing and evaluation scale. According to the findings obtained from the research, it was determined that in-class written expression activities were not carried out in line with the process-oriented writing approach and that the written expression products of the students did not meet the process-based writing criteria.