According to the 2006 Program for International Assessment (PISA), the United States is behind their international counterparts in the areas of mathematics and science. (Darling-Hammond, 2010). The Unites States is at a critical point in developing future leaders in Science, Technology, Engineering, and Mathematics. In preparing students for a competitive global economy being- driven by advances in STEM fields, we can focus on early learning experiences which contribute to positive motivation patterns that, in turn, lead to positive achievement outcomes. This study examined best practices in mathematics achievement in kindergarten and the influences of these practices in the development of mastery motivation and mathematics achievement utilizing data from the Early Childhood Longitudinal Study Kindergarten Class of 1998-1999 (ECLS-K) (n = 21,000). Exploratory factor analyses were conducted to determine clusters of teacher instructional practices. Results revealed that underlying structures of kindergarten classroom instruction include social constructivism mathematics instructional practices, hands on activities, music and movement practices, and child centered evaluation practices. Results from a latent variable path analysis indicated that social constructivism mathematics practices had a positive influence on mathematics achievement overtime. Hands on instructional practices in mathematics had less of a positive influence on student motivation and achievement across the kindergarten, first grade, and third grade academic years. In addition, student's motivation and mathematics achievement at the start of kindergarten had a significant impact on student motivation and achievement across the kindergarten through third grade academic years. Social constructivism practices play a significant role in mathematics achievement during the early childhood years. Implications for early childhood education and teacher training programs in STEM are discussed. [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.]