The purpose of this study is to investigate the corrective effect of physical exercises performed during theoretical classes on the mental performance and attention quality of students. The study evaluated the dynamics of mental performance and attention quality of students before and after completing practical classes in high-complexity disciplines. It also examined the influence of gender on cognitive performance and attention quality during classes and the effect of physical exercises performed during high-complexity practical classes on mental performance and attention. The initial level of mental performance, especially in theoretical high-complexity classes, determines the quality of mental work, the students’ assimilation of educational material, its memorization, and its use during the educational process. A comparative assessment revealed that at the beginning of high-complexity classes, the level of mental performance was higher in students of both sexes in a practical class on the hygienic foundations of physical culture and sports activities. At the same time, female students had a higher level of mental performance and attention in complex practical classes than male students. During classes on human physiology and the hygienic foundations of physical education and sports, students’ mental performance declined. However, the degree of decline in mental performance was greater during the class on human physiology. This phenomenon is attributed to the development of fatigue at the cellular level in the structures of the cerebral cortex. Notably, the fatigue process was more pronounced in female students, especially in human physiology, which is likely explained by the complexity of the subject. After performing physical exercises during classes, there was a moderate decrease in students’ mental performance. Despite the fact that signs of fatigue were also observed during classes on the hygienic foundations of physical culture and sports activities, they were less pronounced than during classes on human physiology and were limited to an increase in the number of errors in the proofreading test, which indicates a decline in attention quality.