Introduction: Speed-strength performance is important during human movements such as jumping, sprinting, and change of direction (COD) tasks, which are a substantial part of sports practice. Sex and age seem to influence performance output in young persons; however, few studies have focused on the influence of sex and age measured via standard protocols of performance diagnostics. Method: Therefore, the aim of this study was to investigate the influence of age and sex on linear sprint (LS), COD sprint, countermovement jump (CMJ) height, squat-jump (SJ) height, and drop-jump (DJ) height performance in untrained children and adolescents via a cross-sectional analysis. This study comprised 141 untrained male and female participants 10–14 years of age. Results: The results showed the influence of age in male participants on speed-strength performance, while in female participants, age did not significantly influence performance parameters. Moderate to high correlations between sprint and jump performance (r = 0.69–0.72), sprint and COD sprint performance (r = 0.58–0.72), and jump and COD sprint performance (r = 0.56–0.58) were found. Discussion: Based on the data from this study, it appears that the growth phase of age 10–14 does not necessarily lead to improvements in athletic performance. To ensure holistic motor development, female subjects in particular should be provided with specific training interventions with a focus on strength and power.