Longitudinal factorial stability and growth of foundational reading skills in at-risk and non–at-risk kindergarteners

Abstract This study examined the longitudinal factorial invariance and growth trajectories of a Spanish curriculum-based measurement (CBM) of foundational reading skills in kindergarten within a Response to Intervention (RtI) framework. A total of 196 Spanish-speaking kindergarteners were assessed at three time points (fall, winter, and spring) on five CBM tasks targeting phonological awareness, alphabetic knowledge, print concepts, and vocabulary. Longitudinal confirmatory factor analyses supported the factorial stability of the IPAL-EI across the kindergarten year, revealing a coherent latent construct with a stable internal organization and demonstrating configural, metric, and scalar invariance. Hierarchical linear modeling revealed significant linear growth across the school year for most CBM indicators and for an omnibus composite score, with the exception of phonological awareness and written language knowledge–text. At-risk students showed significantly lower initial performance across most measures; however, growth trajectories were largely parallel across groups, with limited evidence of differential slopes over time. Despite overall gains in both groups, performance differences between at-risk students and students not at risk remained relatively stable across the school year. These findings provide empirical support for the longitudinal reliability and developmental responsiveness of Spanish CBM scores, particularly for the composite score, underscoring their utility for universal screening within RtI frameworks in transparent orthographies.