Decisions by markers about quality in student work remain confusing to most students and markers. This may in part be due to the relatively subjective nature of what constitutes a quality response to an assessment task. This paper reports on an experiment that documented the process of decision-making by multiple markers at a university who assessed the same written student assessment responses. The paper analyses the professional conversations between those markers around their conceptions of quality in the student assessment responses. It was found that the markers appeared to share common understandings of quality in the context of the marking criteria and standards across the achievement levels awarded. However, despite these apparently shared notions of quality, in some cases different levels of achievement were awarded to the same student assessment responses. This suggests that that there is a clear need for explicitly stated standard descriptors for each level of achievement and that this must be interpreted through substantive professional conversations in the context of real student work. The key driver is the student work, and conversations amongst markers about what constitutes "quality" in the context of the written and explicit criteria and standards of achievement that are available to students and markers alike are a necessity. (Contains 4 tables.)