Based on the aforementioned things, we decided to examine if the choice of content (tasks) the solution of which emphasizes the skills of critical thinking can be used to influence its development in elementary mathematics education, and if that development has anything to do with students’ overall achievement. If the results would confirm this assumption, then teachers would have a more secure footing and clearer orientation in designing and organizing elementary mathematics education, they would be more successful in achieving the requirements for the development of students’ critical thinking, thus making an important step toward overall improvement of mathematics education