A theoretical approach is presented which makes it possible to compile efficient computer programmes for teaching general educational subjects. The programmes are based on model representations of the knowledge to be finally acquired (such models are in fact sets of all possible problems and tasks corresponding to a particular subject, and of their solutions). The models are used for making up training exercises, performance of which would lead to development of the desired knowledge. It is discussed at which stages the use of computers is especially effective, and which forms of computerized instruction are counterproductive and are therefore to be avoided. The approach is illustrated by a computer programme for teaching Russian in the V-th form.