This case study describes the leadership of a school counselor in implementing positive behavioral interventions and supports (PBIS) in a low-income, diverse elementary school with a modest level of external supports. After initiating a grade-level pilot program, the school counselor partnered with university-based consultants to expand the PBIS initiative to all grades. This article presents data from multiple measures of implementation fidelity to illustrate the 5-year process of bringing school-wide PBIS to scale.