BACKGROUND: We examined whether standardized test scores and grades are related to risky behaviors among low-income minority adolescents and whether social networks and social emotional factors explained those relationships. METHODS: We analyzed data from 929 high school students exposed by natural experiment to high- or low-performing academic environments in Los Angeles. We collected information on grade point average (GPA), substance use, sexual behaviors, participation in fights, and carrying a weapon from face-to-face interviews and obtained California math and English standardized test results. Logistic regression and mediation analyses were used to examine the relationship between achievement and risky behaviors. RESULTS: Better GPA and California standardized test scores were strongly associated with lower rates of substance use, high-risk sexual behaviors, and fighting. The unadjusted relative odds of monthly binge drinking was 0.72 (95% confidence interval, 0.56-0.93) for 1 SD increase in standardized test scores and 0.46 (95% confidence interval, 0.29-0.74) for GPA of B- or higher compared with C+ or lower. Most associations disappeared after controlling for social-emotional and social network factors. Averaged across the risky behaviors, mediation analysis revealed social-emotional factors accounted for 33% of the relationship between test scores and risky behaviors and 43% of the relationship between GPA with risky behaviors. Social network characteristics accounted for 31% and 38% of the relationship between behaviors with test scores and GPA, respectively. Demographic factors, parenting, and school characteristics were less important explanatory factors. CONCLUSIONS: Social-emotional factors and social network characteristics were the strongest explanatory factors of the achievement-risky behavior relationship and might be important to understanding the relationship between academic achievement and risky behaviors.