Student tardiness continues to pose a significant challenge within educational institutions, affecting not only individual academic performance but also classroom dynamics and instructional continuity. In the context of the Philippine education system, factors such as transportation limitations, household responsibilities, and habitual lateness contribute to this persistent issue. This single-subject case study explores the implementation and impact of a structured positive reinforcement strategy aimed at reducing tardiness among 18 Grade 11 STEM students at Pasig Catholic College during the 2023–2024 academic year. These participants were selected through purposive sampling for their chronic lateness. Using an A-B-A research design across three distinct phases: baseline observation, intervention, and withdrawal, the study employed tangible incentives to reinforce punctuality and monitored behavioral trends using attendance records and visual analysis. Results demonstrated a marked decrease in tardiness during the intervention week, with sustained improvements even after the withdrawal of external rewards, indicating a potential for habit internalization beyond simple compliance. The study concludes that a straightforward, low-cost positive reinforcement strategy is a highly effective and practical tool for classroom management. It not only swiftly corrects the behavior but may also foster intrinsic motivation and self-regulation in students. The study concludes that such interventions offer a practical pathway to foster self-regulated behavior and a more productive learning environment.

Keywords: tardiness, positive reinforcement, punctuality, classroom management, single case study, behavioral intervention, student behavior, tangible rewards