As a result of the changing notions of work, schools are increasingly acknowledging that they have a strong responsibility in guiding students not only in their academic growth, but also in their career development. This paper presents the results of a study about the effects of teacher training on career dialogues promoting career competency development in students. For the quantitative part of the study, a quasi-experimental research design was used to measure effects among 2291 students. Video recordings of conversations were used to do qualitative research. The results show that only when off-the-job training is followed by on-the-job coaching, the professionalising of teachers proves to be effective as measured on student level. Students notice that the guidance conversations are more appreciative, reflective and activating and that they focus more on self-image development, work and career action. The observations made with regard to the guidance conversations also show that these conversations become more career related.