The authors describe their experimental study carried out with the boarding school pupils of the 3-rd form. The study has shown that the mode of organization of learners' activity influences considerably their mastering the method of the grammar problem solving. The learning work in a dyad turned out to be, on an average, more productive than, the individual one, and the cooperative framework was more favourable comparing with the competitive one. Instructing the cooperating dyad members to perform, respectively, the roles of the executor and of the adviser and controller affected positively the learning process and results. Teaching the pupils, in advance of the joined work, the methods of job communication has also been found an important factor in raising the level of co-operation and, as a result of it, in the efficiency of their learning activity.