Though job opportunities in science, technology, engineering, and math (STEM) continue to expand in the United States, people on Individualized Education Programs (IEPs) while in school are continually disadvantaged in future STEM-based career possibilities. Studies have shown that students on IEPs are far less likely to major in a STEM degree program in college or hold a job in the STEM workforce. Prior to the study, a literature review was conducted, which showed the effectiveness of guided inquiry approaches for IEP students. This mixed methods study examined the factors that influenced the self-efficacies of IEP students in their science classes and what interventions would ultimately improve how these students perceive their abilities to do science. To increase IEP students' self-efficacy in science, teachers engaged students (n=7) with a guided inquiry approach to teaching their classes with significant populations of IEP students. Students then reflected on their experiences in lessons with and without the instructional practice to measure their self-efficacies. Results showed 57.1% growth in student self-efficacy scores, as reported by an observer survey. Students also self-reported lower feelings of negative self-efficacy beliefs after the intervention. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]