Higher levels of self-determination are related to better life outcomes for students with disabilities. Yet the current measures of self-determination available were developed in the 1990s and were developed and tested for a specific disability group. This limitation creates issues with cross-disability group comparisons of self-determination and does not allow comparisons between students with and without disabilities. The development of the Self-Determination Inventory System (SDIS) will address this problem by developing a valid self-determination assessment for a range of disability groups and for youth and young adults without disabilities. The research team will develop, refine, calibrate, and validate the computer adaptive test of the SDIS for youth and young adults with and without disabilities. The research team will also develop, refine, calibrate, and validate a computer adaptive version to be completed by the teachers or parents of the youth or young adult with or without disabilities. Three thousand six hundred students with and without disabilities aged 13–22 years will participate in the study. Another 1,600 teachers, parents, and other adult caregivers will complete the adult SDIS. The SDIS will focus on four characteristics of self-determination: autonomous functioning, self-regulation, self-realization, and psychological empowerment.