This dissertation explores why students in Confucian culture are typically high-achieving on international assessments. Based on ecological system theory, I chose three core microsystems—family, school, and out-of-school learning opportunities—and investigated their intercorrelations as well as associations with academic achievement in different cultural contexts. This dissertation is comprised of three individual studies that investigate different research questions related to the three microsystems. First, I applied LPA to compare the characteristics of schools situated in Confucian and Anglo cultures with respect to disciplinary climate and school resources and found that Confucian students were 15% more likely to study in high discipline schools than Anglo students. Second, I utilized SEM to compare the mediation of disciplinary climate in the relationship between family SES and science achievement in Confucian and Anglo cultures. The result showed that disciplinary climate in Confucian culture explained about 3% more in the total association between family SES and science achievement compared to Anglo culture. Third, I explored whether out-of-school learning is interacted with formal schooling and how out-of-school learning variously predicts students’ science achievement across the two cultural clusters and found that attending out-of-school learning opportunities is positively associated with science achievement. The three analyses thus bring new insight into the relationship among family, school characteristics, out-of-school learning opportunities, and students’ science achievement in a cross-cultural context.