This study measures the success of the implementation of a Cooperative Learning Environment program and presents the results of that program as carried out in three elementary schools and two secondary schools in San Diego, by replicating studies conducted elsewhere in the United States. Whereas the earlier studies document the positive effects of such programs on achievement of the desired outcomes of integration (such as cross-ethnic friendships) and on academic learning, results in the San Diego study did not find similar statistical differences. Possible reasons for the lack of results from pre- to postprogram implementation in San Diego are: (1) pretest scores were high; (2) districts in other studies did not have the same kind of integration and race/human relations background as San Diego; (3) inconsistent implementation; and (4) the short time of implementation. The following are recommended: (1) a more rigorous implementation over a longer period of time; (2) that teachers new to the program be well taught in the use of cooperative learning strategies, and be given sustained in-class resource support, recognition, and support by the site administration; (3) that recognition be given to and use made of role model teachers expert in using cooperative learning environment methods; and (4) that the program be evaluated rigorously, including monitoring of implementation. (RDN)