The study was designed to find out the leadership behaviours of head teachers and its impact on school discipline at secondary level in Punjab. The major objectives of the study were to identify the leadership behaviours of head teachers at secondary level, to explore the existing condition of school discipline, to find out the impact of leadership behaviours of head teachers on school discipline and to compare the leadership behaviours of head teachers gender and locality wise. Three separate and self-constructed instruments were developed for the stud. The interview protocol was designed for head teachers to find out the leadership behaviours of head teachers and school discipline. One questionnaire was designed for teachers to explore the leadership behaviours of head teachers and other questionnaire for students to examine the existing condition of school discipline. Simple random sampling and convenient sampling techniques were used to collect data for the study. The province of Punjab was divided into three zones. Two districts were selected randomly from each zone and 144 secondary schools were chosen from six randomly selected districts of the Punjab. The selected districts were Attock, Sargodha, Shaiwal, Gujrat, Bahawalpur and Layyah. Thirty-six head teachers, 432 secondary school teachers and 2304 secondary school students were selected as a sample of the study. The collected data was entered into SPSS files. To interpret the quantative data, frequency, mean score, standard deviation t-test of independent sample and regression analysis techniques were applied. To analyze qualitative data, the researcher transcribed the interviews, find sub themes and themes of the data to generalize the results. The findings revealed that democratic leadership behaviour received highest rating, while autocratic leadership at second rating. Autocratic and democratic leadership behaviours of head teachers had a positive impact on school discipline. Laissez-faire leadership behaviour of head teachers had not a significant impact on school discipline. Gender wise comparison indicates that there was no significant difference in the opinions of male and female teachers about leadership behaviours. Locality wise comparision also shows that there was no significant difference in the opinions of rural and urban teachers about leadership behaviours of head teachers. Discipline condition of schools was satisfactory at secondary level. It is recommended that head teachers should adopt democratic leadership behaviour to maintain schools discipline in a constructive and positive way.