Background: This systematic review aimed to synthesize recent evidence on interventions to increase moderate-to-vigorous physical activity (MVPA) content of physical education (PE) in children age 8 to 11. Methods: A search of 6 databases was conducted in December 2019. Controlled intervention studies were included so long as they used objective measures of MVPA. Methodological quality was assessed using the appropriate Joanna Briggs Institute (JBI) Checklist. Random effects meta-analysis was used where appropriate. Results: Of the 5459 records, only 5 studies met all inclusion criteria, reporting on 1452 participants; 3 quasi-experimental studies and 2 RCTs. All 5 eligible studies reported favorable intervention effects. Meta-analysis was possible from 4/5 studies: the mean difference between intervention and control groups at follow-up was +14.3% of lesson time in MVPA (confidence interval [CI] 2.7 to 25.8). Conclusions: Efforts to increase the MVPA content of elementary school PE are achievable. Two studies employed PE specialist teachers and 1 study used an expert instructor as their intervention, 2 studies worked with the class teachers using self-determination theory. All studies focused on health (MVPA) outcomes and included either "fitness infusions" or physically active games to engage students' in physical activities and increase their activity level.