This study is expected to determine the impact of a program based on the cooperative learning methodology. This, in comparison to a traditional learning situation in both mathematics and language achievement. The study was carried out on a group of fourth grade students of primary school. In addition, it tried to find the differential impact according to the cognitive style in the field dependence-independence dimension. This work was carried out with 76 students of the Colegio José Martí I.E.D. (Bogotá--Colombia) ranging from 8-12 years of age. The control group received a traditional teaching methodology and the experimental group received the cooperative learning program, composed of 35 sessions (from July to November 2009). All the participants were tested in mathematics and language performance, before and after the intervention. All of them were tested in cognitive style as well. The results suggested that the cooperative learning methodology benefited importantly the academic achievement of the students in mathematics in contrast to the competitive and individualist situations. The results also suggested that the three cognitive style groups were positively affected from the cooperative learning situation. These results were not found in the language area.