ABSTRACT: The purpose of this study was to assess the effectiveness of school principals‘ approaches on management of students‘ discipline in public secondary schools in Migori County, Kenya. The objective of the studywas to determine effectiveness ofpositive behaviour reinforcement on students discipline and establish factors influencing effectiveness of school principal‘ approaches on students discipline in public secondary schools in Migori County. The studyadopted a cross-sectional survey design with a population consisting of 271 principals, 271 deputy principals, 1759 teachers and 10 Sub-county Directors of Education (SCD). Simple random sampling pegged at 30% was used to select 74 principals, 74 deputy principals, 74 student leaders, 8 SCDs and 317 teachers from Krejcie and Morgan; a total of 473 respondents. Primary data was collected using 2 questionnaires; one for Principals and deputy principals, and the second one for teachers while an Interview Schedule for SCDs and FGD guide for student leaders. Piloting, involving 10% from each category of the respondents, was done to determine reliability and validity of the research questionnaires. Test-retest method was used to establish reliability by employing Pearson‘s r with a reliability threshold of .70 and above. Validity was determined by experts in Educational Management and Policy. Quantitative data was analysed using frequency counts, percentages, means, standard deviation and T-test while qualitative data was coded, transcribed and organized thematically. Research ethics were observed during both data collection and reporting of findings. The study established that positive behavior reinforcement was very effective (mean = 3.51) as thevariable had positive and statistically significant correlation with management of student discipline. Findings of this study may be important to educational administrators, policy makers and planners in understanding how positive behavior reinforcement approachis effectively used to manage students‘ discipline