Students with learning disabilities are among those most likely to have difficulties in math, often lacking the knowledge, skills, and understanding foundational to mathematics. Although the concepts, goals, scope, and sequence of curricula are explicit, a coherent conception of how learning progresses is lacking as are valid and reliable formative and summative assessments that provide meaningful, timely, and actionable diagnostic feedback on performance. This project integrates principles of the Bear Assessment System with Universal Design for Learning to develop and validate learning progressions and an aligned, universally designed formative and summative classroom assessment system for promoting conceptual understanding of number sense/operations for students with Math Learning Disabilities. We describe our design and development process and results from our second pilot study.