This study presents a large-scale empirical investigation of reading dispositions and behaviors involving 42,517 elementary, middle, and high school students in Seoul, conducted amid the rapid digital transformation. Reading disposition was measured across five constructs: reader agency, reader beliefs, attitudes toward print/digital reading, and social reading. The findings reveal that as grade level increased, students’ attitudes toward print reading and their reader beliefs tended to decline, whereas their attitudes toward digital reading increased. Overall reading disposition reached its lowest point among second-year middle school students. Female students demonstrated significantly higher reading dispositions across all constructs, particularly in attitudes toward print reading and social reading behaviors. A significant positive correlation was observed between reading disposition and reading behavior, indicating that affective factors act as key mediators of actual reading time and volume.