The rising teacher attrition rates coupled with the challenges associated with the millennial teacher dynamics have heightened the need to address the teacher shortage crisis. Millennial age teachers encompass the largest growing generation cohort serving in the teacher workforce. While many district and school leaders have orientation and onboarding practices designed for new teachers, the effectiveness and quality vary tremendously. The New Teacher Center is a comprehensive mentoring program that aims to support high need districts with teacher induction. To address teacher attrition problems, a quantitative experimental inquiry design was conducted in this study to analyze the effects of the New Teacher Center's comprehensive mentoring program on teacher performance, professionalism, and retention. [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.]