Most empirical knowledge on the processes and challenges of conducting youth participatory action research (YPAR) in the school setting stems from research in the US; only a few studies exist among European youth. In addition, what youth participation looks like in YPAR is rarely described. The present study investigates the experiences of implementing a Junior-researcher YPAR initiative from the perspectives of students and teachers in five ninth-grade classes in Norway. We also observed two of the classes throughout the process. The findings from interviews and observations showed that the Junior-researcher mostly promoted a sound experience of participation and knowledge production among the students. However, students and teachers were not familiarized with a YPAR designed to promote unstructured learning methods and student autonomy, or to limit teacher involvement. The present results illustrate some of the challenges youth participatory approaches may face in a school context.