The goal of this research was develop the quality of education in secondary schools. School effectiveness is important because Thailand is committed to personal development and uses education as a tool to meet this goal. Therefore the quality of education is important and it is
influenced by the leadership of the school administrator. The researcher wanted to study administrators’ leadership affecting the effectiveness of secondary schools. The purposes of this research were: 1) to study secondary schools administrators’ leadership, 2) to study the effectiveness
of secondary schools, 3) to study the relationship between administrators’ leadership and the effectiveness of secondary schools, and 4) to create a prediction equation of administrators’ leadership affecting the effectiveness of secondary schools. The sample of this research was a group of 312 teachers who are heads of department under the Secondary Educational Service Area Office 17 in academic year 2017 and was selected by purposive sampling. The research instrument used was a 2 - part five - rating scale questionnaire. The first part was a 45-item questionnaire about administrators’ leadership. The second part was a 45-item questionnaire
about school effectiveness. The 2 parts had an alpha-coefficient of 97 and 98 respectively. The statistics used for data analysis and hypothesis testing were: mean, standard deviation, Pearson Product - Moment. Correlation Coefficient and simple regression analysis.
