This case study asks readers to consider what leadership actions might help to sustain success for immigrant students in a small urban high school when the leader leaves. Principal Michael Perez, the founding principal of Romero High School, has been recruited to become the superintendent of a first-ring suburban district with rapidly changing demographics. Describing himself as a hands-on "humanistic" leader, Perez established innovative curriculum and organizational structures at Romero High School to meet the language learning needs of the school's teenage immigrant students. His impending departure requires Principal Perez, school district leaders, and his successor to determine what knowledge and skills are needed to sustain school improvements and navigate the leadership succession process.