Focusing on a public elementary school, this study examined key factors that drive the im plementation of school-wide positive behavioral support (SW-PBS) within a collaborative life guidance model that actively engages all members of the school. This research targeted a small-scale institution composed of 58 students and 28 faculty members distributed across seven classes, and the investigation focused on a whole-school application of universal support—tier 1 of the multilevel PBS framework. To explore the factors and challenges associated with PBS implementation, this study collected data from interviews, participatory observations, and documents. Student behavior logs and self-report questionnaires were also used to evaluate changes in student conduct throughout the intervention. The analysis of the implementation process revealed six major factors: a decision-making system, data, practices, equity, outcomes, and contextual factors. The most prominent challenge identified was the need for faculty and staff to consistently encourage students, which often involved material incentives. This difficulty was largely attributed to a lack of philosophical understanding and emotional investment in PBS principles at the institutional level.