The problem addressed in this study was general education teachers' limited confidence for and engagement in evidence-based instructional strategies for inclusion. The purpose of this quantitative descriptive and correlational study was to (a) determine the levels of general education teachers' sources of efficacy, school support, efficacy and outcome expectations and classroom practices with regard to inclusion; (b) examine how sources of efficacy and school culture relate to and predict general teaching efficacy and specific teacher efficacy for differentiated instruction, and outcome expectations for collaboration; and (c) identify how these measures relate to and predict teachers' self-reported practices for inclusion, differentiated instruction, and collaboration. A sample of 145 general education teachers participated in the study, completing an online survey measuring all variables of interest. Respondents reported moderate levels across most variables. The variables of experience, passion, and school support for inclusion were the significant predictors of general teaching efficacy; teacher autonomy and passion were significant predictors for outcome expectations for collaboration, and passion was the only significant predictor of teachers' efficacy for differentiated instruction. Teachers' reported inclusion practices were predicted by professional development, passion, and general teaching efficacy; their collaborative practices were predicted by professional development, passion, and autonomy, and their differentiated instruction practices were predicted by experience, passion, and teacher efficacy for differentiated instruction. Teacher passion served as the single consistent significant predictor for all efficacy and outcome expectations and all classroom practice variables. The null hypotheses were rejected. The sources of efficacy identified as significant predictors of efficacy and practices support aspects of Bandura's theory. Findings can help school districts and teacher preparation programs in developing resources to equip current and future teachers with skills needed to improve inclusion practices. The study should be replicated using a larger sample, and further investigation of the important role of passion revealed in this study should be conducted. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]