In the thesis we analyse and compare the results of students for similar problems at the national assessment of knowledge of physics (NPZ) and at the Čmrlj competition. Based on these data we infer whether on average the tasks at the national assessment of knowledge are more or less demanding than the problems at the Čmrlj competition. Further we are addressing the question of the participants at the Čmrlj competition: are there only the most successful students in the field of physics participating or is the participation in the competition more general, not directly dependent on the previous interest and success of a student in the field of physics. The sample includes high school students attending the school competition and students attending the NPZ. The analysis is supplemented by our own study: two groups of the ninth grade pupils at two randomly selected schools were solving a test, composed of pairs of similar problems from previous NPZ tests and Čmrlj competitions.