In response to low achievement in mathematics at a middle school, an ethnomathematic approach was used to teach coordinate planes. Whether there were achievement differences between students taught by the culturally sensitive approach and those taught by a traditional method was studied. Data were collected from the coordinate planes unit examination for prealgebra students, and the mean scores of those in the experimental and comparison groups were compared. The significance of the statistical difference between the two groups provides evidence that the use of the ethnomathematics software in concert with traditional teaching practices can increase student success in learning about coordinate planes. Three appendixes contain supplemental information about student mathematics achievement. (Contains 1 table, 4 figures, and 15 references.) (SLD)