The purpose of this study is to answer this question: Which is academically superior for young children, full-or half-day kindergarten? This inquiry-oriented case study was designed to compare and contrast students who attended half-day versus full-day kindergarten programs in a suburban public school district. The study is necessary because the issue of full-day versus half-day kindergarten is a current concern that has many stakeholders worried about the quality of the early childhood programs that exist within this school district. Additionally, the research on this subject is out of date. Most previous studies in this area were conducted in the 1980s and 1990s. The theoretical framework for this study is the science of data-driven decision making. Many educational institutions are just beginning to use this process to make fundamental changes to programs and policies. According to Kowalski, Lasley, and Mahoney, authors of "Data-Driven Decisions and School Leadership" (2008), rational decision making is the standard in scientific professions, and therefore this process should be normative in education. Without such rational decision making and without data as a basis for solving educational problems, education is reduced to a craft. The needs for young people in K-12 settings will only be met if professional decision making occurs. Through the use of pre-and post-assessments, the researcher collected reading data from a full-and half-day kindergarten program at an elementary school within a suburban public school district. The reading data included phonemic awareness, vocabulary, and comprehension scores. By comparing the results, the researcher concluded that the full-day kindergarten program did not show overall higher scores than the half-day kindergarten program. [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.]