The State of Illinois adopted the Illinois Learning Standards for Mathematics on June 24, 2010 as a means for students to succeed in college, in a career and in life. The new standards had instructional shifts in content and practice that differed from the 1999 Illinois Learning Standards. The new mathematics standards contained fewer topics for most grade levels. The topics narrowed the focus at each grade level, following a mathematical learning progression. However, there was an expectation for teachers to deeply delve into grade level content standards using the mathematical practice standards for students to become proficient in mathematics by the end of each school year. Some mathematical topics were eliminated from grades where traditionally taught and moved to grades where teachers had little or no experience or background in teaching these topics. The implementation of the new state mathematics standards left many elementary teachers unprepared to effectively teach new math content along with the mathematical practices. New English language arts standards were adopted at the same time, requiring most elementary teachers to learn new content in two core subject areas. This ex-post facto study using mixed methods and correlational design examined the effectiveness of implementing new instructional mathematics coaches in a suburban school district during a school year and the impact they had on student achievement and teacher self-efficacy in mathematics. The study examined state and local mathematics assessment results in grades three through five, along with the survey results from teachers who participated in the study to determine whether the collaborative efforts of the instructional coaches were effective. The findings validated that the instructional mathematics coaches had a positive impact on student achievement and teacher self-efficacy. [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.]