Student-directed projects are a promising approach to supporting powerful learning, yet uncertainty about how to assess these projects presents a barrier to widespread incorporation in K-12 classrooms. Drawing on interviews with computer science teachers and an interdisciplinary literature review, Karen Brennan, Sarah Blum-Smith, and Paulina Haduong offer four principles to guide assessment of student-directed projects: recognizing the individuality of the learner, illuminating process, engaging multiple perspectives, and cultivating capacity for personal judgment. They describe the research behind these principles and provide and example of what they look like in practice.