To argue tactfully is a goal in argumentative writing, which entails balanced argumentation schema. Although computer-supported collaborative learning (CSCL) has been widely acknowledged as language learning mediation, especially in writing, few studies investigate its effectiveness in activating the balanced argumentation schema. This study explores the effectiveness of QQ group discussion, a kind of CSCL mediation most popular in China, in argumentative writing by means of quasi-experiment and interview. Fifty-six second-year college students in an English Department participated in this stu...