The purpose of this study is to theoretically discuss a specific aspect of teachers' responsibilities: their responsibility for pupils' or children's well-being. We ask two interrelated questions: firstly, how might (Swedish) teachers' sense of responsibilities for their pupils' well-being be understood in relation to ethical theory? Secondly, what does this insight bring to the discussion of teachers' professional responsibility within the global discourse of educational policy that increasingly stresses accountability and efficiency in an "age of measurement?" Education can be described as an intervention in a pupil's life, motivated by the idea that it will somehow improve it. When one implements this intervention, from a legal/political perspective, it boils down to a series of responsibilities assigned to teachers, as expressed in current policy documents. However, an exploration of empirical examples in a Swedish context of teachers' sense of responsibility for their pupils' or children's well-being, expressed in everyday situations, indicates that the matter is complex. In order to find tools with which to better understand such expressions, we turn to the field of ethics. A thorough inquiry into the various reasoning regarding responsibility reveals that responsibility as socially defined and given is not sufficient to capture the intimacy and relational uncertainties of the teachers' stories, which is why we turn to the writings of Lévinas and his ethics of responsibility. His ethical language helps to capture relational processes that cannot be predefined and that are based on an infinite sense of responsibility for the other person. We continue by discussing and problematising the increasing demands for measurability and accountability in the field of teachers' professionalism. Here, we illuminate risks involved with the movement towards the fixed and calculable, since it overlooks the intricate ways in which teachers' given and felt responsibilities are woven together.