Despite proliferated efforts to integrate computer science in elementary education, there is a dearth of studies that synthesize the current state of CS education research in formal educational contexts, specifically in upper elementary classrooms. Further, while numerous studies have investigated approaches and strategies that broaden participation in computing, the majority of them focus on secondary and post-secondary settings. The present study uses a systematic literature review process to review research conducted with students in formal classroom settings in grades 4, 5, and 6 and published since 2013. We review the research through two questions: What are barriers to broadening participation in CS in upper elementary (grades 4-6)? What instructional approaches and strategies help broaden participation in CS in upper elementary (grades 4-6)? A systematic search of the literature highlighted approaches used for broadening participation, including using various teaching media, designing scaffolds in instruction, and integrating into other subject areas. We conclude by identifying gaps in the research and identifying areas for further research.