Deciding on grades holds significant authority in the Swedish teaching profession. Grading teachers must be certified and have decision-making power not possible to override by any authority or client. However, the professional autonomy is circumscribed by the obligation to ensure national consistency in grading by making decisions based on generally expressed grading criteria formulated by the Swedish National Agency for Education. Additionally, teachers are required to “specifically considering” national test results in several subjects in secondary school. In addition, comprehensible and formative expressed transparency in assessment and grading, communicated through digital portals that teachers often are obligated to use, is expected by employers and pupils/parents.This study, based on semi-structured interviews with secondary school teachers combined with analysis of informal and formal assessment documentation, explores how professional discretion takes shape in grading decisions given demands for national consistency in grading and external communication about the basis for assessment and decisions. More explicitly, the professional principles grading teachers adhere to in making their decisions, how they are communicated and how this generates decision-making processes, and final decisions is in the focus of this study.Preliminary results identify three levels of professional principles: firstly, formal principles closely aligned with national regulations; secondly, local principles shaped by school-specific approaches of how to organize the work at the school where the teacher is employed, and thirdly, individual principles unique to each teacher. Depending on these principles, diverse various approaches to assessment and communication emerge, governing the teacher’s professional space between discretion and automatization.