Mathematics Achievement Test (MAT) was used for post-test in the study. The treatment (X) was Student Team-Achievements Division Cooperative Learning (STAD, CL) teaching strategy. In this strategy mathematics teachers in experimental schools used past learners’ performance to constitute teams of five to six members based on mixed ability gender and ethnicity. Teachers in the experimental schools were expected to follow a guideline provided by the researchers, which was aimed at ensuring uniformity of treatment. The control Groups (C1 & C2) were taught through the conventional teaching methods. The topic was taught at the same time to all the groups to ensure uniformity and comparability of results.