Three main purposes provided the foundation for this study. The first purpose was to investigate academic achievement through analyses of data obtained through formal and informal assessments among kindergarten through eighth grade students who participated in a Head Start program, center-based care program, or home-based care prior to school entry by gender, ethnicity, and socioeconomic status. The second purpose was to determine whether early childhood program participation has an effect on academic achievement as students progress through school. The third purpose was to examine similarities and differences in formal and informal assessment data as predictors of achievement through investigation of specific math and reading skill attainment by gender, ethnicity, and socioeconomic status based on program participation. A non-experimental quantitative research design was employed in this research study, as a causal-comparative or ex post facto research approach allowed retrospective investigation of cause-effect relationships in determining long-term academic achievement based on early childhood program participation. In the present study, archival data obtained from the National Center for Education Statistics (NCES), specifically the Early Childhood Longitudinal Study-Kindergarten Class of 1998-1999 (ECLS-K) were analyzed for six rounds (i.e., fall and spring of 1998-1999, 1999-2000, 2001-2002, 2003-2004, and 2006-2007) of formal and informal measures of reading and math achievement. For each of the six rounds of data analyzed, children who attended center-based care programs outperformed children who participated in home-based care, and considerably outperformed children who attended Head Start in kindergarten through eighth grade. Further, of the 918 analyses, 729 were statistically significant. Additionally, girls consistently outperformed boys in reading for each round of data analyzed and boys surpassed girls in math performance as they progressed to upper grade levels. Furthermore, White and Asian students outperformed Black and Hispanic students in reading and math in kindergarten through eighth grade. In addition, students from middle-to-upper socioeconomic standing consistently outperformed students from more disadvantaged backgrounds from kindergarten through eighth grade. Moreover, teacher ratings of specific measure of student skills were consistent with formal assessment results. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]