The study seeks to ascertain whether co-operative learning model is equally effective for students with mastery and performance goals. The study uses quasi-experimental and factorial design for conducting the experiment. The experiment was conducted on 153 students of standard IX studying in schools affiliated to the SSC Board and with English as the medium of instruction. It has used two tools, namely, achievement test in mathematics and learning goals inventory both developed by the researcher. The researcher has also developed an instructional programme for co-operative learning. The techniques used to test the hypotheses include the ttest, ANOVA and ANCOVA. The study found that the effect of the co-operative learning model on students’ academic achievement is maximum. Co-operative learning model was found to be more effective for students with mastery goals whereas the traditional lecture method is found to be more effective for students with performance goals