Deficits in strength of the lower extremities and postural control have been associated with a high risk of sustaining sport-related injuries. Such injuries often occur during physical education (PE) classes and mostly affect the lower extremities. Thus, the objectives of this study were to investigate the effects of balance training on postural sway, leg extensor strength, and jumping height in adolescents. Twenty high school students participated in this study and were assigned to either an intervention (n = 10) or control group (n = 10). The intervention group participated in a 4-week balance-training program integrated in their physical education lessons. Pre- and posttests included the measurements of postural sway on a balance platform, jumping height on a force platform, and maximal isometric leg extension force on a leg-press. Balance training resulted in significantly improved postural control, increased jumping height, and enhanced rate of force development of the leg extensors. Physiological adaptations rather than learning effects seem to be responsible for the observed findings. These results could have an impact on improving the performance level in various sports and on reducing the injury prevalence of the lower extremities.