Following the seminal writing of James Coleman (1988), a number of scholars have suggested that inequality in child and adolescent development reflects differences in social capital among families from different backgrounds (e.g., Sampson, Morenoff, & Earls, 1999; Crosnoe, 2004; Kao, 2004). By "social capital," Coleman referred to relations of trust and shared expectations in a social network of children, parents, and educators. A key marker of social capital is "intergenerational closure," that is, whether the parents of children in a friendship relation have a relationship themselves, so that social ties link parents as well as their children. Questions about social capital are especially salient for Latino families. Several studies have noted that a sense of isolation from school systems often perceived by Latino families is a key barrier to the school success of Latino children (Stanton-Salazar, 2001; Valenzuela, 1999). Efforts to test for social capital effects have largely been stymied by problems of endogeneity and unobserved heterogeneity (Mouw, 2006). Does social capital promote child development, or do positive relations emerge among parents and between families and schools when children are thriving in school? The best way to test for causal effects would be to randomly allocate persons to social networks, but that is not feasible. Instead the authors' approach is to randomly assign schools to an intervention that is designed to promote social capital among families and between families and schools. Because of their interest in Latino families, they selected two communities with large Latino populations: Phoenix and San Antonio. To manipulate social capital, the authors employed a widely used intervention, Families and Schools Together (FAST). FAST is a scientifically tested program designed to develop relations of trust and shared expectations among parents, teachers, and children (McDonald, 2002; McDonald et al., 1997; McDonald et al., 1991; McDonald & Frey, 1999). Findings are as follows: (1) Assignment to FAST led to intensified parent-parent and parent-school social networks in Phoenix, where school-level effect sizes on four measures ranged from 0.09 to 0.35. (2) Assignment to FAST did not have this effect in San Antonio; effect sizes are close to zero except in the case of the number of staff respondents would feel comfortable approaching, where the effect size is -0.19. (3) FAST effects on child outcomes across cities mirror those on parents: in Phoenix, children in FAST schools exhibited fewer behavior problems and more prosocial behavior than those in control schools, whereas this pattern is not evident in San Antonio except in the case of parent-reported peer problems, which follows the expected result. In general, outcome differences between FAST and control schools are more pronounced in teacher reports than in parent reports. This may reflect a response bias among teachers, who were not blind to condition, or it may reflect differences in FAST effects on behavior in the school as compared with the home setting. The possible mediating role of social capital, and of FAST effects among those who attended FAST sessions, will be examined when data from both cohorts are available and results will be included in the conference paper. (Contains 1 table and 2 figures.