Students with autism spectrum disorder (ASD) are a growing population within schools. Teachers and staff need to be adequately prepared, as well as confident in working with this unique group of students. The purpose of this study was to ascertain the Colonial School District teachers' perceptions of their preparedness and self-efficacy regarding working with this group of students based on their perceptions of the effectiveness of their teacher preparation programs and professional development participation. Additionally, the study sought to determine if there is a significant relationship between teachers' preparedness and self-efficacy and their education level, years of experience, and grade level taught. Through this study there were several major findings. First, it was found that there is a statistically significant, positive relationship between the following factors in regard to working with students with ASD: perceived effective of teacher preparation programs and perceived preparedness; perceived effectiveness of professional development workshops and perceived preparedness; and perceived preparedness and perceived self-efficacy. Additionally, it was found that differences between groups of teachers' perceptions of preparedness and self-efficacy based on their years of experience, grade level taught, and education, are not statistically significant. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]