Critical thinking is considered to be one of the most important abilities which help us to solve problems, evaluate arguments, interpret limitless information, choose criteria or make decisions in everyday life. Every person needs to use critical thinking therefore it is important to develop students` critical thinking in all classes including Physics. We summarize various definitions of critical thinking and we describe a survey, where students solve problems whose solution requires the use of critical thinking. We proposed five problems with the physics content and five problems without it. We compare students` results in each section to see if they can solve problems without physics content with better successfulness than the problems with physics content. We also compare the solutions of students from different grades to see how the school attendance impact the development of critical thinking. After all we compare the results of two groups of students – those who are studying at primary school and those who are studying at primary school for intellectually gifted children. Our data suggest that students might have statistically better results solving problems without physics content and that school attendance might have a positive impact on the development of critical thinking.