Math anxiety can have an extraordinary impact on middle level students' ability to learn. However, certain classroom practices may be able to mitigate this impact. In terms of assessment practices, proficiency-based learning, also called competency-based learning or standards-based grading, may help establish a learning environment that either prevents the development or decreases the influence of anxiety for middle level mathematics students. The present study analyzed the relationship between specific characteristics of proficiency-based learning and students' anxiety about mathematics. Using a multiple case study design, we examined the practices in two middle level mathematics classrooms and how they related to the experiences of five students in those classes who self-identified as having math anxiety. We focused specifically on the practices of establishing clear learning objectives, implementing assessment for learning, providing effective feedback, promoting reflection, and providing opportunities for reassessment. Data collection included interviews of students and teachers, in-class artifacts, and class observations. We found that reassessment was the characteristic of proficiency-based learning most closely associated with alleviating students' anxiety. We also found that math anxious students can benefit from effective feedback and clear learning objectives, particularly when presented simultaneously.