In a sample of 466 Chinese high school students, we examined the relationships between Chinese high school students' stress in the school and their academic achievements. Regression mixture modelling identified two different classes of the effects of Chinese high school students' stress on their academic achievements. One class contained 87% of the students. In this class, the students' stress negatively predicted their academic achievements. For the other 13% of the students, their stress did not predict their academic achievements. Furthermore, we found that gender did not moderate the relationships between Chinese high school students' stress in the school and their academic achievements. (Contains 2 tables.)