**2.3. Participants**

Participants in this study are 18 educators, each of which had a prominent role in leading a comprehensive, large-scale change process that aims to foster students' HOT by implementing thinking-rich instruction. Eight participants are (or were until recently) National Subject Superintendents who are responsible for curriculum development and implementation, for professional development, and for assessment in a specific school subject across the whole school system. Four participants have (or had until recently) prominent roles in the development and implementation of programs in the area of teaching HOT on the national level, and three participants had a similar role on the district level. Two participants have leading pedagogical roles in a large school network, and one participant is an academic who has been deeply involved in national efforts to improve learning and instruction in a specific school subject. Because all participants are well-known educators who could easily be identified and because confidentiality was promised to the participants, all details (such as names of programs or subject domains) were omitted from the quotations used throughout this chapter.

The selection of participants applied the following criteria:

