خلاصة:
Introduction: This paper reports the results of an investigation on the effect of cooperative learning (STAD style) on academic achievement.Materials and methods: Sampling of the study consists of 80 (22-23 years old) students at a state university in Iran. Levels of pre-knowledge acquired by the students were evaluated by means of a self-developed instrument. A clear significant difference, as a conclusion, was detected in favor of the experimental group indicating the success of the STAD. Results: it is found that cooperative learning helped students to develop some of their educational and psychological skills, because the cooperative activities encouraged students to interact freely and communicatively and consequently increasing their academic achievement in Developmental psychology and Physiological psychology courses to a higher level. But it seems conventional teaching hardly improves the teaching of concepts and academic achievementConclusion: in non-cooperative classrooms, in which conventional teaching are used faculty members often talk most of the time and only a few of the brightest learners have the opportunity to participate, usually by responding to the teacher. So, it is found that experimental group students taught by cooperative learning are more successful than control group students taught by conventional teaching.