After we performed initial measurements of the development of critical thinking in both student groups, we introduced the experimental program into the experimental group, whereas the control group continued working in the usual manner. The experimental program was realized through 27 exercises consisting of prepared tasks, the solution of which emphasized skills of critical thinking (formulation of the problem, reformulation of the problem, evaluation and sensitivity to the problem). Within one exercise, all tasks were focused on one skill of critical thinking. We provided an equal number of exercises for each component of critical thinking, and within each exercise, an approximately equal number of tasks per skill of critical thinking.