This study examines whether [Reading App], an adaptive, personalized game-based program designed to help young learners build a foundation for reading comprehension and literacy, can improve early reading skills for pre-kindergarteners and kindergarteners (N = 402 treatment, 690 comparison). This study measured the feasibility of implementing [Reading App] in classrooms, teacher and student experiences of using the application, and growth in literacy outcomes between students in classrooms using [Reading App] and students in classrooms not using the application, controlling for baseline performance. Results of hierarchical linear models showed that: (a) kindergarteners who used [Reading App] made significantly greater gains on end-of-year literacy assessment than the comparison group, especially in alphabet knowledge and (b) pre-kindergarteners who mastered at least 16 alphabet skills in [Reading App] experienced greater gains in the skill than comparison group peers. Teacher surveys and interviews suggested that [Reading App] is an easy-to-use, effective, engaging learning resource that empowers them to provide personalized instruction and foster a more equitable classroom environment. The study provides initial evidence of [Reading App]’s effectiveness as a program that can enhance educators’ capacity to address learner variability and provide personalized instruction for all learners.