Introduction. In recent years, research studies have demonstrated a significant decrease in physical activity (PA) amongst young people. Most of the young generation participate in sport and recreation too rarely, and they devote too much time to passive leisure. Diagnoses of physical activity at different stages of our lives, with particular emphasis on children and adolescents, are increasingly indicating that along with age, the level of physical activity, especially during leisure time, is decreasing. Material and methods. The aim of the study is to compare selected parameters of physical activity on a single day among students aged 12 and to determine how these parameters differ at school and at home. The study was conducted using an ActiGraph WGT3X accelerometer on a group of 100 students (50 girls and 50 boys) in a rural area of southern Poland. Results. The analysis showed that for parameters such as vigorous activity, total moderate-to-vigorous physical activity (MVPA), and step count, the observed difference between the time spent at school and outside of school was statistically significant (p < 0.05). All of these parameters were characterised by a higher level during school time. On the basis of the analyses performed, it was concluded that the school environment contributes to increasing youth’s physical activity. Effective educational programmes promoting physical activity in different forms should be addressed to youth as well as to parents (custodians), who are responsible for the physical development of their children.