The aim of the research was to determine the effect of an 8-week circuit training program on explosive strength and strength endurance in physical education classes intended for high school students. The research included 60 students of two second-grade high school classes. Both classes attended regular physical education classes, where, within the main part of the class, one class had a special program for developing strength through circuit training (circuit group), while the other one had no modifications to the regular physical education program (control group). The classes were randomly marked as circuit group (n = 28) and control group (n = 32). Five strength tests were used in the study: squat jump, countermovement jump, squats, push-ups, and sit-ups. The results showed that the 8-week strength development program organized as circuit training contributed to a significant improvement in strength. The results of all tests showed a significant effect of training on students' strength. It has been determined that short-term circuit training in physical education classes is an effective way to develop students' physical performance.