During the 2000s the educational policy discourse was sharpened, and the dominant learning discourse set the agenda. Policy programs and educational reforms seek to optimize learning by focusing on the teacher and demands for “high professionalism.” High teacher professionalism, it has been argued, promotes learning and is combined with functions, often concisely expressed as, for example, “learning management” and “digital formation.” Although this much-hyped political rhetoric is criticized, it is necessary to define appropriate concepts of professionalism as well as clarification on the significations of teacher practice, teacher role, and didactical functions. The meaning and consequences of changing demands for teacher professionalism appear during the process of “didactization.” Based on research findings from long-term fieldwork, a cross-case analysis is presented, drawing on Danish examples from 1980 to 2020. The examples referred to are: (a) the interdisciplinary and project-oriented university environment (from the 1980s); (b) developments in elementary school (from the 1990s); (c) IT classes in upper secondary school (from the 2000s); and (d) online learning and e-pedagogy in a nursing education program (from the 2010s). An overview of the spectrum of changing teacher functions and contemporary challenges is provided.