In this study, the effects of a school improvement program on cooperative learning (CL) with respect to the elaborations of 6th grade students working in mixed ability and mixed sex dyads on 2 cooperative tasks were examined. A post test only design with a control group was used to investigate the provision and receipt of elaborations within the dyads and the performance of the dyads working on cooperative mathematics and language tasks. Treatment dyads were found to exchange significantly more high level elaborations during the language task than the control dyads. The treatment dyads also tended to produce higher performance scores on the 2 tasks. The present study borrows from the Piagetian and Vygotskian perspectives on development stressing the importance of social interaction for learning based on the active reconciliation of different perspectives within the cooperative group and the importance of studying learning as a social process. From the cognitive elaboration perspectives of Webb and Farivar (1999) and King (1999), it borrows the view that students in small groups have to verbalize their inner thoughts and learn more by providing elaborated help and learn less by receiving less elaborated help. In the present study, the effects of a CL school improvement program on the interactions of students working in dyads were examined. The program was aimed at guiding the teachers in the development of the instructional behaviors necessary to conduct a cooperative lesson. It is assumed that the program should not only affect the instructional behaviors of the teachers but also the quality of the student interactions while working in small groups.