This study assessed student activity levels, lesson contexts, and teacher behaviours within the revised English National Curriculum for Physical Education (NCPE). Fifteen Year 7 (age 11-12 years) PE lessons were systematically observed for each gender using SOFIT (System for Observing Fitness Instruction Time). Boys engaged in moderate-to-vigorous physical activity (MVPA) for 59.7 percent of lesson time compared to 46.1 percent for girls (p less than 0.0001). Most MVPA was accrued during the NCPE lesson range and content theme of Outwitting Opponents (63 percent), and the least during Accurate Replication lessons (38.7 percent; p less than 0.0001). Students participated in most MVPA during game play lesson contexts within the Outwitting Opponents and Exercising Safely and Effectively themes. Less MVPA was evident during management and general knowledge lesson contexts. Achievement of MVPA is a worthwhile PE goal but is influenced by a range of social, environmental and pedagogical determinants, the latter of which can be modified by teachers. (Contains 3 tables.)