Developing a Vertically Scaled Assessment of Elementary Students' Number Sense.

This article focuses on the development and validation of a brief assessment designed to measure mature number sense in U.S. students in grades 3–5. Mature number sense is defined as the ability and inclination to flexibly and efficiently use understanding of numbers and operations to solve problems, operationalized through four components: number concepts and magnitude, multiple representations, effects of operations, and mathematical equivalence. The 24-item electronic assessment, administered within about 10 minutes, was developed to be practical for classroom use and linked via common items to an existing assessment for older students, enabling vertically scaled scores to track development from grades 3 through 12. Validation evidence from multiple studies supports that student responses reflect mature number sense strategies, scores are reliable, internally consistent, fair across demographic groups, and distinct from timed arithmetic fact fluency measures, while sharing the same factor structure as the older-student assessment. The authors emphasize that the assessment is intended for informal monitoring and research rather than high-stakes evaluation and highlight future research directions to further validate and apply the tool in educational settings.