K-3 Interstellar Express System Technical Manual

The Interstellar Express Assessment System (IEAS) is a technology-enabled, K–3 early literacy screening and assessment system designed to identify students at risk for reading and language difficulties, including dyslexia, while supporting efficient, developmentally appropriate universal screening within MTSS frameworks. IEAS comprises a battery of brief, tablet-based assessments targeting automaticity, phonological awareness, decoding, spelling, and oral language skills, delivered through fixed-form and computer adaptive formats. Each task requires approximately 2–3 minutes, with adaptive algorithms minimizing testing burden while maximizing classification accuracy. The system yields norm-referenced scores, developmental scale scores, and two screener-based indices: Potential for Word Reading Success (PWRS) and Dyslexia Risk Indicator (DRI).Psychometric evaluation was conducted using data from 4,099 students in kindergarten through grade 3 across five U.S. states. Item banks were calibrated using multiple-group two-parameter IRT models, followed by adaptive testing implementations. Results demonstrate moderate to strong empirical reliability across measures, strong convergent and concurrent validity with established standardized assessments, and excellent classification accuracy for predicting end-of-year word reading outcomes (AUCs frequently ≥ .90). Differential test functioning analyses indicate largely invariant performance across race/ethnicity, gender, and language status. Collectively, findings support IEAS as a reliable, valid, and efficient early literacy screening system suitable for large-scale educational implementation.