This article draws on a recent New Zealand study of how young people learn to think critically about the past when they conduct internally assessed course work. The research demonstrated that, although students can develop advanced understandings of historical thinking when they conduct research projects, this development is largely dependent on how well teachers understand the conceptual nature of historical thinking. Teachers who understand how the discipline of history operates are more consistent and accurate in making judgements, able to provide specific feedback to students during the research process and they structure their assessment tasks to reflect historical thinking concepts. In the high-stakes internal assessment environment of NCEA understanding how the concepts of historical thinking drive teaching and learning at this level matters. It provides a robust, disciplinary framework that teachers can draw on when they are judging students’ work. This framework equips them to have the confidence to mark holistically when this is appropriate and to see the criteria as a guide.