Performance goals are important predictors of high school students' academic achievement. Identifying the factors that influence these goals can significantly enhance students' academic performance. This study uses a questionnaire to survey 39,953 high school students in a province in central China. It focused on two key external sources--parental and teacher support. The study also explored the mediating role of learning motivation in the relationship between students' perceived parental and teacher support and performance goals. The findings from the structural equation model show that perceived parental and teacher support both positively influence students' performance goals. In addition, both external and internal motivation partially mediate this relationship. Notably, internal motivation plays a stronger mediating role in the case of perceived teacher support. This suggests that teacher support has a greater impact on students' performance goals than perceived parental support. These results provide empirical insights for improving educational support strategies. They highlight the importance of promoting both academic motivation and performance goals in high school settings.