The present study was conducted to examine the effect of underachievers’ mathematical communication with peers on their mathematical achievement and self-efficiency. Mathematical communication with peers can be defined as mathematical knowledge or their own thoughts such as mathematical concepts, problem solving strategies to talk to peers. Sixteen mathematics underachievers selected from the fifth grade at an elementary school were split into two groups: one was an experimental group, and the other was a control group. A total of fourteen instruction sessions were given to each group, and addition and subtraction of fractions in the number-operation unit were taught in the sessions. Mathematical communication with peers was emphasized in the experimental group, while, in the control group, mathematical communication was conducted between the teacher and students. The results of the study are as follows. First, there was no significant difference between the experimental group and the control group in relation with mathematical achievement; however, the students performed better in the post test compared to the pre test. The experimental group demonstrated a significant increase in the sentence-type questions and a significant decrease in the no-response reaction. It can be explained through the fact that mathematics underachievers in the experimental group improved mathematical communicative competence through intervention. Second, the self-efficiency score of the experimental group showed a significant progression compared to the control group. Discussion on mathematics underachievers' mathematical communicative competence was also presented.
Key words : mathematical communication, mathematical communication with peers, self-efficacy, fractional arithmetic, word problems, mathematics underachiever