Previous research reported differences in student self-determination based on disability status. Specifically, students without disabilities consistently self-report higher self-determination compared with their peers with disabilities, suggesting differential opportunities and supports for self-determination exist within school contexts. To further examine potential differences in student self-determination, the present study examined the impact of an evidence-based practice designed to promote student self-determination, the "Self-Determined Learning Model of Instruction" (SDLMI), on student self-determination outcomes when implemented in inclusive, secondary core content classrooms as a universal (i.e., Tier 1) support across an academic year. Findings suggested a relatively small change in overall self-determination during the first year of a multiyear study, but consistent patterns across students with and without disabilities. Implications for research and practice are discussed.