The action research describes the process of how the Counselling Self-Efficacy Scale for Teachers (CS-EST) was developed and explores its suitability as a teaching and learning tool using a pilot study of 178 students at Tallinn University, Estonia. The study integrated action research, interdisciplinary project-based learning, scale development and adaptation principles. During six counselling courses the SC-EST has been used both from the third-person perspective of the action researcher to reflect on the learning outcomes of students and from the student's first-person perspective to support reflecting on one's own counselling skills. The study showed that counselling self-efficacy in prospective teachers significantly raised during the courses. The scale can be used as an online self-assessment task in conjunction with reflective journaling during university-level counselling courses, as the study showed that together they form a useful formative assessment tool. The SC-EST seems to be suitable for Estonian and international students, however larger international studies are needed to further validate the scale. I consider the action research as a transformative learning experience in my professional development.