Development of ROAR Morphology: Initial Validation of a Real-Word Suffix-Based Assessment of Morphological Knowledge

Morphological awareness contributes to literacy development through multiple components, yet few assessments with established evidence of internal construct structure are widely available and suitable for whole-class administration for efficiently characterizing elementary students’ suffix-based morphological knowledge in written sentence contexts. This study reports on the development and validation of ROAR Morphology, a brief classroom-based assessment of suffix-based morphological knowledge in written sentence contexts for students in grades 2–5, administered in under 10 minutes to whole classrooms with automatic scoring. Items were designed to capture a learning progression of suffix-based morphological knowledge, varying suffix type (inflectional/derivational) and suffix commonality (common/less common), with careful attention to cognitive processing demands including number of derivational distractors. Calibration of response data from 735 students using Rasch modeling yielded high reliability (α = .91; with fit indices ranging from .79 to 1.22). Item difficulty analyses confirmed that derivational morphology was more challenging than inflectional morphology, and less common suffixes were more difficult than common suffixes. Cognitive processing demands, specifically the number of competing derivational distractors, contributed additional variance in item difficulty beyond linguistic features. Based on item difficulty modeling, we established four empirically derived learning progression waypoints reflecting proficiency with suffix-based morphological structures of increasing complexity, from foundational inflectional morphology with common suffixes to more complex derivational morphology with less common suffixes. Notably, base word characteristics did not drive item difficulty, confirming that the waypoints capture genuine differences in suffix-based morphological knowledge development. ROAR Morphology uniquely predicted literacy achievement beyond word reading and sentence reading measures (ΔR ² = 7.2%, p < .001), supporting its discriminant validity. These findings demonstrate that suffix type, suffix commonality, and cognitive processing demands systematically influence suffix-based morphological knowledge development in written sentence contexts, and that empirically validated waypoints may inform instructional planning during the critical grades 2–5 window when this knowledge is rapidly developing.