ABSTRACT: International educational reformation has recommended the importance of
investigation to enhance mathematics learning and develop mathematical power for children
(Quinnell, 2010). This research used a qualitative approach involving teacher and student
participation in junior high schools (state school and private school owned by an educational
foundation) in Indonesia which applied group investigation based learning in mathematics
class. The results showed that mathematics learning with investigation approach (group
investigation) had succeeded to transform negative disposition into productive (positive)
disposition and to enhance productive disposition toward mathematics and had affected the
increasing of students’ mathematical power. The students' mathematical power ability
appeared in the reasoning actualization (providing reasons, mathematical communication in
groups and connections between ideas in mathematics when they discussed about the
investigation result. Result of this study was also in line with Flewelling and Higginson (2003)
that investigation, and problem solving suggested an opportunity for students to use their
imagination in order to obtain more powerful mathematics ideas and understanding about
relationship between mathematical ideas.