There is a compendium of research to support the premise that positive teacher-student relationships (TSR) set the stage for children's success via classroom engagement, social functioning, and academic skills development. Although studies have demonstrated reciprocal associations between TSR and academic achievement, inferences that stem from prior study results are limited due to methodological designs that fall short in capturing directionality in developmental change processes. To address gaps in the literature and improve our understanding of the complex associations between TSR and academic achievement, we analyzed the codevelopment of TSR and achievement in reading and mathematics using dual change score models (DCSM), a type of latent change score model, focusing on the associations between longitudinal trajectories of TSR-achievement pairs and on the reciprocal prediction of latent changes between each wave of measurement. We examined data from a large-scale, nationally representative study (Early Childhood Longitudinal Study Kindergarten Cohort of 2010-2011). Results of our DCSM, contrary to prior findings, demonstrate that variability in the ratings of TSR did not predict subsequent latent changes in reading or mathematics achievement. Likewise, the variability in achievement scores did not predict subsequent latent changes in ratings of TSR. Limitations and future directions for research are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).