Mathematics course in vocational high school education is significant worldwide to equip vocational students with the technical and personal skills that are required for the effective workforce as discussed in the context of Science, Technology, Engineering and Mathematics (STEM) education. The present research sets out to investigate Turkish maths teachers' believes and instructional practices through comparing vocational students' perceptions for mathematics instruction and the researcher's observation in a state vocational high school. A total amount of 20 maths teachers and 161 students participated in this longitudinal study (n=181). Mixed methods were used, and three types of data were collected: questionnaires, interviews and observation. The findings indicated that maths teachers' belief and practices were not consistent when compared with the questionnaire and interview data collected from vocational students, and also observation carried out by the researcher.