Introduction: The beneficial properties of sports in all areas of a person's activity is an indisputable fact, regardless of their gender or age. The active effect of sports on his mental performance can be considered as the indirect result of well-being, but the duration of playing sports before the appearance of these beneficial effects is questionable. Purpose: To investigate the effect of sports on the performance of 5th and 6th grade students. Material and method: Statistical analysis was performed with the help of the statistical program SPSS V28 at a significance level of 5% (p-level=0.05). The data were drawn from the official grades of 1st , 2nd and 3rd semester of 63 students of the 5th and 6th grade primary school in southern Attica. It was also recorded whether they participated in sports activities before the first semester, between the first and second semester and between the second and third semster 2021 – 2022. As the data collection was census no sampling technique was applied. Results: The results of the survey showed that an increase in participation is expected to increase the probability of better student performance (H = 22.922, df = 2, p < 0.001) and particularly among the participation time categories "At least 6 months" - "Not at all" and " At least 6 months” – “Up to 3 months” (p < 0.001). The significance of the simultaneous effect of gender (p<0.001) and time of participation (p=0.006) was also found. Conclusions: As expected, the beneficial effect of sports on student performance was found and proved. It was also found that an increase in the time involved in sports is expected to enhance the performance of students more and that the beneficial effects are expected to appear after at least 3 months of involvement in sports.