Examining the Impacts of Integrating Peer Support and Self-Determination for Autistic Youth: Intent-to-Treat Analysis

Autistic adolescents experience poor in-school and postschool outcomes, and there is a need for comprehensive interventions that facilitate student outcomes and build collaboration across general and special education. The Propel Project examined the impact of combining two evidence-based practices—the Self-Determined Learning Model of Instruction (SDLMI) and Peer Supports (PS)—to promote aligned, inclusive systems of support in secondary schools. This paper reports the findings of the preregistered Intent-to-Treat (ITT) analyses comparing the implementation of SDLMI Only, PS Only, and a combined SDLMI + PS model, including a new general educator-delivered SDLMI Plus intervention. Implementation occurred within complex school contexts, and challenges with recruitment and implementation led to reduced sample sizes and limitations in addressing the preregistered research questions. While findings were primarily null, Bayesian Model Averaging (BMA) analyses provided directions for possible patterns to explore further in future research. The challenges also highlight the need to further explore implementation determinants. Implications for future research and practice are provided.