Online distance learning (ODL) has spread worldwide in all levels of education, and academic performance is a frequently mentioned topic in the research of ODL. This research focuses on the impact of students’ prior academic performance in different subjects on their academic performance in the context of transition from a traditional class to online distance learning. The participants are students from a key public high school in China. They took a traditional in-person class in their twelfth grade first semester and took ODL in twelfth grade second semester. Positive and strong Spearman and Pearson Correlation (~0.8) is found between student’s academic performance during traditional class and student’s academic performance during ODL; positive and weak Spearman and Pearson Correlation (~0.4) is found between student’s academic performance during traditional class and the change of student’s academic performance through the transition from the traditional class to ODL, indicating a positive correlation between prior academic achievement and later performance. Linear regression fitting is applied to the student’s academic performance during traditional class and the student’s academic performance during ODL, the results have shown that the prior academic performance represents by cumulative exam have a good prediction of the later academic performance in both traditional class and ODL context.