The teacher's pet phenomenon is widely recognised and negatively viewed by students and teachers. Teachers that favour selected students adversely affect the emotional climate in the classroom, as well as the social development and academic achievements of students. Despite the indicated consequences, the phenomenon is surprisingly rarely studied. Analysis of data gathered from 2164 students and 138 teachers showed that respondents perceived the phenomenon as widespread at each stage of education. Students assessed the phenomenon more negatively than teachers, although this evaluation was modified by respondents' views on two hypothetical types of pets, i.e., pet-leader versus pet-rejected. Teachers perceived the phenomenon negatively in the subgroup that described pets using attributes that are characteristic of leaders, and less negatively in the subgroup that described pets using attributes characteristic of rejected students. This pattern was reversed among students. The similarity between these findings and the results of previous studies suggest that the phenomenon is universal in temporal and spatial terms, and the differences in its reception discovered in various groups of respondents can be described through an inverted, U-shaped function.