The purpose of this study is to better understand the norms, processes, and implications of a standards-based assessment (SBA) system in a project-based, STEM-focused secondary school in the United States. The SBA system had both formative and summative components in relation to classroom teaching and grading, respectively. We focus on both teacher and student perspectives of the assessment system, and the potential impact of the system on their roles as teachers and learners. Results indicate that students reacted positively to the reteach and retake aspects of the SBA system, but also faced feelings of stress due to fluctuations in grades and the demands to stay current in their academic progress. Evidence also shows that the SBA system changed students’ perceptions of the learning process, and themselves as learners. Our study sheds much-needed light on the use of an assessment and grading practice that is severely understudied in K-12 education in the US, and also adds to the database of studies that make explicit connections between teaching, learning, and assessment at the classroom level.