The objective of this study was to examine muscular fitness using measurements of the right hand grip (RHG) and left hand grip (LHG), as well as the counter movement jump (CMJ) performance of both athlete and non-athlete school children. Additionally, the study aimed to compare these variables between genders. A total of 221 school children aged 11-13 participated in this study. The participants were categorized into four groups based on their characteristics: female athletes (n = 57), female non-athletes (n = 60), male athletes (n = 59), and male non-athletes (n = 45). The primary exclusion criteria included any musculoskeletal limitations that could potentially affect test performance. The strength of the RHG and LHG (kg) was assessed using the Takei-TKK-5101 device. CMJ heights (cm) were measured using the Smart-Speed device. For all variables, a mixed-design two-way univariate analysis of variance (ANOVA) was employed to identify differences between and within groups. The findings of the present study indicated that the RHG, LHG, and CMJ values of athletes were significantly greater than those of non-athletes for both genders (p < 0.001). Moreover, the analyzed performance values exhibited significant differences between male athletes and male as well as female non-athletes, and also between female athletes and female as well as male non-athletes (p < 0.001). Engaging in sports is highly important for school children aged 11-13 to enhance their muscular fitness. It can be stated that the development of muscular fitness for both genders would be higher in children who participate in sports compared to those who do not engage in sports.