Coaching school leaders can positively contribute to supporting professional and school development within a challenging societal context (Brandmo et al., 2021; Ritzema et al., 2022). To maximize the effectiveness of coaching for professional and school development, empirical research on influencing factors is essential (Darling-Hammond et al., 2022; Lochmiller, 2021). The professional development trajectory (PDT) for school leaders in Flanders (Belgium) studied existed of training days, individual coaching sessions, and also professional learning communities (PLC) meetings, supported by a coach. This research context with a PDT with a specific approach provided a unique opportunity to examine the role of the coach and the impact of coaching characteristics (Cannon-Bowers et al., 2023; Lofthouse & Whiteside, 2019). Using empirical research, we explored which coach-related characteristics determine professional and school development during the PLC meetings of a PDT for school leaders. Sub-questions were: • Q1: What is the explanatory value of the coach’s didactic approach and coaching skills during PLC meetings on the predefined outcome variables? • Q2: Is there any indication of differences in the didactic approach and coaching skills of PLC coaches that may be associated with differences in outcome variables? • Q3: What is the explanatory value of a PLC coach’s expertise on the outcome variables? • Q4: What characteristics associated with participants, context, ... are mediating for the perceived effectiveness of PLC coaching? The research questions were answered using mixed methods research with an online survey at two moments (n=88%), and focus group discussions with 11 PLC groups (N=15). Finally, each coach (N=7) was interviewed. The descriptive analyses showed that school leaders perceived participation in the PLC as valuable, however, with a large spread in the outcomes. Although the independent variables ‘didactic approach’ and ‘coaching skills’ of the coaches were perceived as above average positive, there was a large spread. These differences were situated in the areas of commitment, goal orientation and tailored support. A coach with a lot of domain expertise and little coaching expertise is perceived by both school leaders and coaches as less effective than a coach with more coaching expertise – ideally PLC coaching – and less domain expertise. Nevertheless, both are important: the existing expertise should be used by the coach in the development process, taking into account possible needs and expectations of school leaders and existing contextual factors.

Brandmo, C., Aas, M., Colbjørnsen, T., & Olsen, R. (2021). Group Coaching that Promotes Self-Efficacy and Role Clarity among School Leaders. Scandinavian Journal of Educational Research, 65(2), 195-211. https://doi.org/10.1080/00313831.2019.1659406 Cannon-Bowers, J. A., Bowers, C. A., Carlson, C. E., Doherty, S. L., Evans, J., & Hall, J. (2023). Workplace coaching: a meta-analysis and recommendations for advancing the science of coaching. Front Psychol, 14, 1204166. https://doi.org/10.3389/fpsyg.2023.1204166 Darling-Hammond, L., Wechsler, M. E., Levin, S., & Tozer, S. (2022). Developing Effective Principals: What Kind of Learning Matters? Learning Policy Institute. Lochmiller, C. R. (2021). Guest editorial: Coaching for improvement in education: New insights and enduring questions. International Journal of Mentoring and Coaching in Education, 10(4), 393-398. Lofthouse, R., & Whiteside, R. (2019). Sustaining A Vital Profession: Evaluation of A Headteacher Coaching Programme. Ritzema, L., Maslowski, R., Bosker, R., van Geel, M., Rekers-Mombarg, L., & Visscher, A. (2022). Behorend bij de deelrapporten van NRO-onderzoek naar bestuurlijk vermogen en professionalisering in het VO.