The aim of this study was to determine the opinions of teachers about the supervisory practices of school principals and the approaches they adopt based on the supervision of teaching practice, professional development and evaluation. It is a mixed method study. It was preferred to include samples from different geographical regions and provinces of Turkey in order to increase the level of representativeness of the sample. Accordingly, the research data were collected from the teachers working at public kindergartens, primary schools, secondary schools and high schools in the provinces of Bursa, Gaziantep, Izmir, Antalya, Samsun, Batman and Eskisehir during the spring semester of 2016-2017 academic year. For the qualitative data, the study group consisted of 28 teachers specified through the maximum diversity sampling method. According to the research results, the opinions of the teachers about the supervisory practices differed in three sub-headings and the qualitative findings supported the quantitative ones. In addition, it was concluded that the principals adopted the bureaucratic approach in the supervisory process based on the means of the responses to the questionnaire.