Many universities are moving to greater use of standards-based assessment to support effective student learning. Implementing a standards-based approach includes involving academic staff in writing descriptions of standards for assessment tasks both to guide the marking process and clarify staff expectations for students. However, recent research shows many students find written descriptions of standards difficult to understand unless they are helped to engage with assignment exemplars. Teacher-led marking and discussion of exemplars in class result in increased student understanding of standards and higher achievement. This mixed-methods study explores students' perceptions of the usefulness of exemplars, and the effects of different teacher styles in leading in-class marking of exemplars. An interactive style in which the teacher provides a balanced explanation of the standards embedded in exemplars is associated with higher student achievement. A minimal institutional approach to implementing standards-based assessment, in which staff simply construct and distribute written grade descriptors to students to support effective learning may have little or no overall benefit, particularly for students transitioning to their first year at university. Staff development activities may need to focus on helping teachers expand their conceptions of the role of assessment for learning while also supporting their development of written assessment standards.