The present research attempted to investigate the impacts of gender and age on the freshly-graduated eighth graders' percentiles in the central high school entrance exam (LGS) in 2020. The sample of this causal-comparative study comprised 6,039 students selected from secondary schools in Isparta who took the LGS in 2020. The data were obtained from the Isparta Directorate of National Education on a chart demonstrating the participants' demographic characteristics and the percentiles of their exam scores. The findings revealed significant differences between the students starting school at 60-65, 66-68, and 69-71 months and those with a school starting age of 72 months and older by exam achievement. In this sense, the students starting school at an early age (60-71 months) had poorer achievement in the LGS than their counterparts starting school at an older age (72 months and above). Moreover, the students' achievement on the said exam significantly differed by gender. Accordingly, the female students demonstrated greater achievement in the LGS when compared to the male students. Considering the findings, it may confidently be asserted that it would be appropriate to amend the provision of the relevant regulation as the minimum age for starting school to be 72 months as of the fall semester.