Due to grades as a primary concern in school selection in China, parents tend to choose a better school when their children enter secondary school from primary school resulting in the changing peer group (reference group). According to the Social Comparison Theory, individuals are affected by comparing with the people around them to get their own evaluation. This study aims at exploring the effects of changing reference group on developments of academic achievement and self-esteem. Results indicated that selecting secondary school with better grades may benefit individual academic performance but bring no positive influence on self-esteem developments.