The article deals with the problem of factors and psychological mechanisms of influence of cooperative learning on students' achievement. On the basis of comparative analysis, four approaches to understanding the factors of effectiveness of cooperative learning are distinguished: motivational, socio-psychological, cognitive-genetic, and cognitive-functional. The motivational approach (D. Johnson, R. Johnson, R. Slavin) brings to the fore the motivation of performing joint educational tasks, determining the structure of rewards or group educational tasks that stimulate and direct the activity of students. The socio-psychological approach (E. Aronson, V. Battisch, D. Solomon, K. Delucci, E. Cohen, S. Sharan, Y. Sharan) emphasizes the cohesion of students, their interpersonal relationships, which depend on the success of educational activities: students actively participate in group tasks and help each other if they identify with the group and strive for joint success. Proponents of this approach attach great importance to ways of forming student groups (teams), establishing constructive interpersonal relationships during joint learning, as well as reflecting on the process and results of joint cognitive activity. Proponents of cognitive approaches believe that interaction between students in itself increases their success due to intensive cognitive processing of information, rather than motivation or social cohesion of students. Two slightly different cognitive approaches are distinguished, which developed in parallel ways: cognitive-genetic and cognitive-functional. The cognitive-genetic approach, which was formed in line with the theories of mental development of L. Vygotsky and J. Piaget, is based on the assumption that communicative interaction in the process of performing cognitive tasks contributes to the mental development of students and increases the quality of assimilation of educational material (M. Burns, B. Wadsworth, W. Damon, F. Murray). The cognitive-functional approach arose in the vein of cognitive psychology and claims that the positive effect of cooperative learning on the success of students is ensured by cognitive restructuring (processing) of educational information, which contributes to its preservation in memory and integration into the previously learned system of knowledge (S. Allen, N. Webb, M. Wittrock, D. Dansereau, L. Devin-Sheehan, A. O'Donnell, A. Palincsar, M. Presley, R. Feldman). Summarizing the results of research in the field of cooperative learning makes it possible to create a coherent theoretical model that integrates various approaches and comprehensively considers the main factors of the effectiveness of cooperative learning: motivation, group cohesion, processes of interpersonal interaction that stimulate cognitive development and processing of educational material. In such a model, each of the four approaches considered plays a role and makes an important contribution to understanding the interrelated processes of cooperative learning.