INTRODUCTION This study examines how the changes in weight status across the spectrum of a senior high school study are associated with academic performance measured by the university entrance exam scores. MATERIALS AND METHODS A unique dataset which compiles a national health examination profile and the General Scholastic Ability Test data bank in Taiwan was constructed. The final sample comprised 149,240 senior high school students of which 70,662 were males and 78,578 were female students. The school-level fixed effect models were estimated. RESULTS Students who were either (a) not overweight in the first year but overweight in the third year of senior high school, (b) overweight in both the first and third year, or (c) overweight in the first year but not overweight in the third year, were more likely to score lower on the university entrance exam, compared with their never-overweight counterparts. The findings differ by gender and test subjects. DISCUSSIONS The change in weight status during senior high school period is associated with subsequent university entrance exam outcome. Students who start senior high school being overweight should be paid attention. School-based programs and practices need to be implemented to reduce the prevalence of overweight among students.