This case study examined the first two years of adult preparation or "readiness" for an elementary school's adoption and implementation of a trauma-informed, social emotional learning (SEL) universal curriculum. SEL programming served as a key lever for improving the academic growth and achievement of students over a 3-year period. The primary objective of the current study was to identify the process used to increase the school's capacity for implementing and sustaining an SEL program. Study 1 examined the utility of a needs assessment conducted in year 1 as a measure of school readiness, which included a leadership questionnaire, observations of school/classroom climate, and focus groups with school community leaders and teachers. Results informed school strengths and key areas for improving capacity to support an SEL program, including indicators of positive climate, expertise-building among teachers and staff, aligning resources and disciplinary policies, and identifying SEL standards. This information guided the types of professional development implemented in year 2. Using artifact review and focus groups, study 2 examined whether the year 2 professional development assisted in improving the targeted school capacities. Most areas indicated improvement, and the changes are likely critical first steps for effectively implementing and sustaining an SEL program.