To ensure the face and content validity of the instruments, the questionnaire was vetted by
two experts in Department of Research and Psychology, Faculty of Education at Chulalongkorn
University. A Cronbach alpha coefficient of .97 was obtained for the whole questionnaire,
demonstrating that it was a highly reliable instrument. Coefficients of reliability of the teachers’
actions on guidance services scale, the teachers’ perceptions of the significance of guidance services
scale, and teacher self-efficacy for delivering guidance services scale were .89, .96, and .87,
respectively