The professional development (PD) of teachers is a perennial issue, about which much has been written in the past decades. In the past, teachers' PD was organized in formal programs aiming primarily at teaching teachers the necessary knowledge to apply in the classroom; however, in practice, teacher learning is more complex. Many studies show that teachers hardly implement the theories they learn in teacher education in their own teaching practices (e.g., Wideen, Mayer-Smith, & Moon, 1998). This problem has been related to student teachers' socialization processes as students in the school system (Hargreaves, 2004) and to the influence of the cognitive frameworks that abound in the teachers' workplaces (Coldron & Smith, 1999; Lasky, 2005). These explanations have led to an improvement of PD activities (cf. Darling-Hammond & McLaughlin, 1995; Lawless & Pellegrino, 2007; Porter, Garet, Desimone, Suk Yoon, & Birman, 2000).
Although effective PD is important to teacher learning, teachers assert that they learn a lot during their everyday work--by doing or by trial and error (Kwakman, 2003; Lohman & Woolf, 200 l)--which has led to increased attention on the impact of teachers' informal workplace learning (e.g., Eraut, 2004; Jurasaite-Harbison, 2008; Marsick & Watkins, 1990). Following Billett (2004), we define informal learning as learning taking place where no PD trajectory or learning community has been explicitly organized to foster teacher learning (cf. Eraut, 2004).
Given teacher claims that their workplace yields significant learning, investigating the efficacy of their informal learning is relevant. In an earlier study, we described 32 experienced teachers' informal learning in the context of an educational reform in which teachers were encouraged to foster active and self-regulated learning (ASL; Hoekstra, Brekelmans, Beijaard, & Korthagen, 2009). This reform required most teachers to change their teaching philosophies and strategies. Interestingly, this study showed that the majority of the teachers did not change, even though they engaged in informal learning activities.
These findings have led to a follow-up study, which is the major focus of this article. This follow-up study zoomed in on the learning process of Nicole, an experienced teacher who had participated in the initial study. Nicole was very inspired by the reform, but her informal learning environment did not support her attempts to change. The quantitative data showed that Nicole's beliefs and behavior had indeed not changed over the course of a year. For the follow-up study, Nicole agreed to receive supervision. In the course of seven supervisory sessions, based on an approach called multi-level learning (MLL), Nicole experienced a major transformation, in terms of both cognition and behavior. Studying the process that Nicole went through, both in the year of informal learning and during the period of supervision, may deepen our understanding of how supervision can support teacher learning in the context of educational change.
The main question addressed in this article is, how does formal learning through supervision differ from informal learning in the professional life of a teacher? This question is answered by addressing the following subquestions:
1. What were Nicole's learning outcomes and informal learning activities during the year she did not receive systematic support in her learning?
2. What were Nicole's learning outcomes after the series of supervisory sessions?
3. What aspects of the supervision contributed to achieving these learning outcomes?
The central notion of learning is conceptualized in terms of both cognition and behavior. Research has shown that teachers' behavior is more crucial for student learning than teachers' cognition, but these two aspects influence each other (Wubbels & Levy, 1993). Hence, we consider both changes in cognition and changes in behavior to be important learning outcomes. …