A descriptive correlational research was designed to identify factors perceived to explain supervision effectiveness of senior secondary school heads of agriculture department in Botswana. A valid and reliable instrument was used to collect data. Findings revealed that, heads of agriculture department were effective in their supervisory roles. Variables that explained supervision effectiveness were adequacy of supervision time, interpersonal qualities possessed, work experience, amount of time spent in other engagements, and amount of time spent teaching. The conclusions drawn from findings of the study were that, adequate time of supervision is important for heads of agriculture department to perform their supervisory roles effectively, and heads of agriculture department value supervision, and therefore, need little supervision from school heads to perform their supervisory roles. The teaching service management in Botswana should consider reducing teaching time for heads of agriculture department to afford heads of agriculture department more time to focus on supervision tasks.
Keywords: Adequacy of Time, Heads of Agriculture Department, Supervision Effectiveness, Supervisory Roles