This study aims to explore the impact of empowerment on school effectiveness and examine more broadly the findings of early research. This mixed study used an exploratory sequential design. The initial stage of research uses qualitative methods followed by the quantitative stage. In the qualitative stage, research data were collected through in-depth interviews with 19 teachers determined by purposive sampling. The research findings at the qualitative stage were then followed up for wider testing using a larger population and sample. A total of 104 teachers were determined as research samples using proportional random sampling techniques from a population of 712 teachers in 39 high schools in North Sumatra Province, Indonesia. Qualitative findings provide evidence that psychological and structural empowerment have the same qualities as employment involvement and that empowering working conditions affects the attitude of teachers that their work is important. They can do work and set choices; have an impact on their departments and tend to show autonomy that generates more energy and ability in their work. Quantitative findings explain that structural empowerment influences psychological empowerment at 45.6% and has influence on school effectiveness at 43.9%. Psychological empowerment has influence on school effectiveness at 64.3%. Structural empowerment has influenced school effectiveness through psychological empowerment of 48.2% and a total influence of 92.10%. Qualitative findings suggest that the strength of structural and psychological empowerment determines school effectiveness.