What is Teachers’ Professional Development

The chapter presents the transformational processes found in a group of in-service teachers who attended an online distance learning professional development program that appeared to be stable two years after the program ended. The program was supported by Mezirow's transformative learning theory, which inspired the program's instructors. The mixed method (quantitate and qualitative) was chosen as the method of data collection. The results indicated that the program activated the critical reflection of the participants on their experiences, transformed their initial perceptions about the teaching of biological concepts in Primary School, and the utilization of DEC and OER in educational practice, encouraged their reflection about their professional role, and enhanced their personal and professional development.