The aim of this study was to assess the interrelations of social support and school attitudes as predictors of achievement across a culturally and economically diverse sample of preadolescent children. Parent and peer support were assessed along with parent and peer attitudes toward school. Achievement indices were the child's own attitudes, grades, Stanford Achievement scores, and teacher ratings of school adaptation and competence. Of particular interest was the extent to which support and attitudes interact with a number of potentially significant demographic factors, including grade level, gender, ethnicity, and school economic level. Findings indicated that parent support and school attitudes were associated with most achievement indices. Friends' attitudes were predictive of children's attitudes, school adaptation, and academic competence. Support from friends was related to higher achievement for low-income and minority children. The findings affirm the importance of the child's social ecology to school performance and suggest that intervention strategies be targeted in this direction. (Contains 14 references.) (EV)