Background: This study was informed by the bodies of literature emphasizing the role of physical education in promoting physical activity (PA) and addressing teacher fidelity to curricular models. Purpose: The purpose of this study was to compare student PA levels, lesson context, and teacher PA promotion behavior among classes where teachers were using the Dynamic Physical Education (DPE) curricular model with low, moderate, and high fidelity. Methods: Participants were 20 physical education teachers, and their 4th and 5th grade students. Each teacher was observed teaching three times during the study. Fidelity data were collected using a validated observation instrument. PA, lesson context, and teacher behavior data were collected using the System for Observing Fitness Instruction Time (SOFIT). Data analysis included descriptive statistics and group difference tests. Results: Significant differences among the three fidelity groups were identified in several items of the observation instrument. No significant moderate-to-vigorous PA or lesson context differences were found among the three groups. Students taught by teachers in the high fidelity group spent a significantly higher proportion of lesson time (7.5%) in vigorous PA than students taught by teachers in the low fidelity group. Teachers in the moderate and high fidelity groups spent a significantly higher proportion of lesson time promoting in-class PA than teachers in the low fidelity group. Discussion: Fidelity of implementation to the DPE model had little impact on student PA. The findings of this study can inform future researchers about the methodological importance of examining teacher fidelity to curricular models and associated outcomes.