Based on an analysis of 137 texts written by pupils, this paper examines pupils' humour directed at teachers, its types and social functions. The collected data are divided into three categories that describe different modes of teachers as targets of pupils' humour. The first mode describes teachers as unintentionally comical, the second as duped by their pupils and the third as intentional users of humour. The analysis focuses on different functions that pupils' humour directed at teachers fulfils in the social life of the classroom. The paper concludes by showing how key functions of social humour (such as creation of solidarity, negotiation of power and realisation of personal needs) are connected to the three modes of pupils' humour directed at teachers.