The understanding that students on varsity baseball teams exhibit lower academic performance amid the growth of baseball in Taiwan is well established. However, some studies have indicated a positive correlation between sports participation and academic achievement. Therefore, this study delved into the causal relationships between baseball-team participation and academic performance among ninth-grade students in Taiwan. It further explored the influence of various background factors based on the three facets of family capital on their academic performance. Data collected from an education longitudinal survey of secondary school students. Through bivariate analysis, factor analysis, and multiple regression analysis, the following findings emerged: (a) Baseball-team students exhibited 47.5 points lower academic performance than non-baseball-team ones. (b)The low academic performance was not exclusively a result of the poorer academic performance of indigenous students. (c)The hypothesis that three dimensions of family capital impact on academic performance was supported. (d) Baseball-team participation contributed to the low academic performance, which was not caused by the low eighth-grade results of the students. They exhibited low BCT scores after their 8th-grade results was controlled.