The Common Core State Standards (CCSS) require a major shift in instructional practices among teachers. Such changes cause much uncertainty as teachers' roles and identities begin to change. Major school reform creates difficulty for school leaders who must develop teacher support and dedication to 'top-down' reform initiatives in their classrooms. Literature suggested that proper support from building and district leaders is needed to reduce the uncertainty caused by such changes. Guided by organizational change theory, the purpose of this study was to examine whether perceived organizational support (POS), perceived environmental uncertainty (PEU), perceived principal support (PPS), and principal and teacher agreement on PPS, significantly influenced teachers' affective commitment (AC), continuance commitment (CC), normative commitment (NC), and overall commitment (OC) to LDC. Furthermore, special attention was given to the mediating effects of principal and teacher agreement on PPS by exploring the relational change it caused between independent and dependent variables. A descriptive-correlational, causal-comparative design was used with modified validated scales for the measurement of respective study variables. Purposive sampling was used and surveys with the scales were distributed to all schools in the State of Arkansas that were using Literacy Design Collaborative (LDC) as their CCSS reform initiative. Results from teachers and principals in 51 schools that voluntarily completed LDC training (n = 51 principals and 196 teachers) were used to answer research questions. The findings showed demographic covariates related to the tenure and educational levels of participants influenced OC; POS, PEU, PPS, and principal/teacher agreement on PPS explained a statistically significant 12% of the variance in AC; principal and teacher agreement on PPS mediated the significant relationships of the independent and dependent variables and had a very large effect size (n[superscript 2] = 0.74) on PPS. Furthermore, findings on principal and teacher agreement did not completely support previous research on Self-other Agreement. Under-estimators were found to have best influence on teacher commitment. It was concluded that garnering commitment to LDC was difficult among longer tenured teachers but more likely among teachers with advanced degrees. Principals should make themselves aware of teachers' feelings about support and uncertainty to garner higher commitment from teachers. [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.]