There is considerable debate about the relative importance of family versus school factors in producing academic and nonacademic student outcomes, and whether and how their impacts vary across different student groups. In addition to critically reviewing and synthesizing earlier work, this study extends the literature by (a) using the ECLS-K, a U.S. longitudinal dataset that follows a nationally representative sample of children from kindergarten through fifth grade to examine the effects of two types of family factors--family process variables (specific things families do) and family status variables (who families are)--on students' academic achievement and nonacademic outcomes; and (b) using the PISA 2006, a cross-country cross-sectional dataset that assesses academic achievement of 15-year-old students in reading, mathematics, and science literacy to compare U.S. students with their peers in 20 other countries and economies in terms of family factors and academic achievement. Specifically, hierarchical models are estimated to account for the nested structure of the ECLS-K data, and interaction models are used to examine whether and how the relationships between family process factors and student outcomes differ by race and socio-economic status (SES). Using PISA 2006, hierarchical linear models with country fixed effects are estimated in the international comparative analysis of academic effects of family factors. Findings of this study suggest that family process factors can have significant impacts on both academic and nonacademic outcomes. Results of the U.S. data indicate that even after controlling for demographics and school inputs, student achievement was associated with multiple dimensions of family process factors including parental expectations and beliefs, learning structure, resources availability, home affective environment, parenting and disciplinary practices, and parental involvement. Furthermore, several family process variables (including doing homework more frequently, having home Internet access, and owning a community library card) had higher returns in terms of student achievement for black children or children from low socio-economic families than for their counterparts. Family process factors as a whole hold some value in explaining nonacademic outcomes. Results of the international comparative analysis suggest that U.S. students did not fare as well as their peers in other countries and economies, and that family process variables, especially considered collectively, were important factors in explaining student achievement in an international setting. Appendices include: (1) Variables Measuring Family Process Factors in ECLS-K; (2) Scale Items and Reliability Coefficients; (3) Descriptive Statistics: Waves 2-5; (4) Family Process Factors by Race/Ethnicity: Waves 2-5; (5) Correlations Between SES and Reading/Mathematics Test Scores; (6) Correlations Between SES and Family Process Factors: Waves 2-5; (7) SES by Family Process Factors: Waves 2-5; (8) Coefficients of Unconditional Models; (9) Coefficients of Interaction Models; (10) Scale Items and Reliability Coefficients; (11) Correlations Between SES and Teacher SRS [Social Rating Scale] Scale Scores; (12) Coefficients of Unconditional Models; (13) Education Production Function and Econometric Estimation Strategies; (14) Specification Tests; (15) OLS Coefficients of Baseline and Family Process Models; (16) Tobit Coefficients of Baseline and Family Process Models; (17) Tobit Coefficients of Interaction Models; (18) PISA [Program for International Student Assessment] 2006 Countries and Economies; (19) Variables Measuring Family Process Factors in PISA 2006; (20) Achievement Test Scores by Country; (21) Coefficients of Unconditional Models; and (22) Coefficients of Interaction Models. (Contains 80 tables, 2 figures, and 80 footnotes.) [This document was submitted as a dissertation in December 2009 in partial fulfillment of the requirements of the doctoral degree in public policy analysis at the Pardee RAND Graduate School (PRGS).]