Resumo. ABSTRACT This study aimed at evaluating the association between class context and the teacher’s behavior with the physical activity (PA) level of Elementary School students during Physical Education (PE) classes. Eighteen PE classes from six schools were assessed. Class context and the teacher’s behavior were measured based on systematic observation, that is, by using the System for Observing Fitness Instruction Time (SOFIT), whereas the students' PA level was measured with accelerometry. Data were treated with descriptive statistics and shown as the percentage of the class time spent in sedentary behavior and at different PA levels. The association between class context and the teacher’s behavior with different PA levels was assessed by applying binary logistic regression. The percentage of students with regard to the structured games (35.8%), skill practice (23.2%) and management (21.7%) represented 80.7% of PE class total time. General instructions (45.5%), management (28.7%) and observation (18.3%) were the most frequent teacher’s types of behavior seen. It was found that the percentage of time students spent in sedentary behavior and at different PA levels during PE classes varied according to the class context and the teachers' behavior.