Fraction knowledge predicts higher-order mathematics. Valid measures are crucial for understanding its developmental trajectory. This accelerated longitudinal study designed and validated grade-appropriate versions of the Fraction Knowledge Assessment (FKA) and examined children's development from 2nd to 6th grade. Methods: We measured the fraction knowledge of 342 children. We assessed FKAs reliability, validity, and factor structure and used Item Response Theory (IRT) to calibrate item difficulty and link across versions. Then, we investigated longitudinal changes in children’s fraction knowledge. Results and Conclusion: All FKAs had good internal consistency and concurrent validity, and fit well with a one-dimensional model. IRT analyses revealed a shift from fraction magnitude items discriminating students in early grades, to operation items discriminating students in advanced grades. Development was more pronounced from 2nd to 3rd than from 5th to 6th grade, aligning with local curricula. We share the FKA versions to support further research and educational practice.
Starling‐Alves et al. (2025) studied this question.