Abstract
Abstract The difficulty in learning algebra is mostly blamed to the discrepancy between arithmetic lesson in elementary school and algebra lesson in middle school. Hence, a bridge is needed to connect those two core subjects thorough a pre-algebraic lesson. This study is aimed to generate an understanding of how the students’ shift from arithmetic to algebraic thinking during pre-algebraic lesson. It is a part of a larger study in design research to establish a learning trajectory in pre-algebraic lesson by using pattern investigation. The data were gathered from written works, video registrations and field notes in 32 fifth grade students’ of an elementary school in Palembang. The data were analyzed qualitatively using constant comparative method. The result showed that the students’ shifting from arithmetic to algebraic thinking is highly impacted by their clarity in seeing geometrical structure of a pattern. Hence, it is recommended for the teachers to conduct a pre-algebraic lessons using pattern investigations visualized in geometrical representation for the elementary school students