The international FIRST® LEGO® League (FLL) Challenge robotics competition is designed to promote students’ STEM interests and experiential development of 21st Century skills. This paper reports on the findings of a qualitative interpretivist multiple case study PhD project which examined the lived experience of FLL Challenge robotics coaches and student teams in Perth, Western Australia. It compares students’ self-reported perceptions of their 21st Century collaboration and communication skill development with their actual learning and team processes during the 2021 competition season, as observed by their coach and a non-participant researcher. Students reported positive impacts of competition participation on their team’s skill development; however, coach and researcher observations suggest that social and teamwork challenges meant that these improvements were not necessarily demonstrated to the same extent by all team members. Students’ skill development during the season was influenced by individual team members’ expertise, skills, and attitudes; and their coaches’ facilitation of reflective team building tasks.