The primary purpose of this study was to analyze the link between students' expectancy beliefs, subjective task values, out-of-school activity, and moderate to vigorous physical activity (MVPA) participation across secondary school physical education (PE) classes. The sample comprised 96 students (58 girls, 38 boys; Mage = 15.03, SD = 0.94) from schools located in Northeast Finland. The self-report questionnaire was modified to address the domain-specific questions for Finnish PE. Accelerometers were used for the objective assessment of students' MVPA across the PE classes and during out-of-school activities. The findings show that perceived importance indicates MVPA involvement for girls and attainment value and out-of-school MVPA for boys. Boys were more physically active than girls across PE classes. In contrast, girls received more out-of-school activity across the 7 days. The major cause of concern arising from the current findings was that girls engaged in up to 26.2% and boys 33.6% of their weekly MVPA during only two 45-min PE classes. A higher priority needs to be placed in schools on encouraging young people to engage in daily physical activity and providing guidance that makes it easy to find activities in which girls and boys have opportunities to be successful and feel competent. Schools should also use PE as a mean to promote greater physical activity outside of school.