Despite the movement toward identification of evidence-based practices (EBPs), there is a discrepancy in the availability of school-based EBPs targeting the unique needs of students with high functioning forms of autism and related social needs. Based on calls for systematic intervention development and evaluation processes, the current study describes the manualization, feasibility, and effectiveness testing of the school-based Social Competence Intervention for Adolescents (SCI-A) curriculum. School personnel were trained to implement SCI-A to a targeted student population. Fidelity and social validity data indicated curriculum feasibility and acceptability within secondary school settings. Student social functioning, executive functioning, and theory of mind demonstrated postintervention gains with moderate effect sizes. Results are promising for SCI-A's continued positive trajectory within the phases of EBP evaluation research. Challenges for intervention effectiveness testing within schools and future considerations for evaluating EBPs are discussed.