Philosophy with Children is a highly dialogic form of teaching and facilitation plays an important part in ensuring dialogic quality. During the philosophical dialogue, the facilitator estimates from the participants' behaviour whether the dialogue is engaging, collaborative, and meaningful to the participants. However, little is known about facilitator assessment of participants' experiences and how this assessment correlates with participants' experiences of the learning environment. Our study examines five facilitators' experiences from 58 online philosophical dialogues for school children and compares facilitator perceptions with participant and observer experiences. The results indicate that children can experience synchronous online dialogues as meaningful, collaborative, and supportive, but that facilitators have a tendency to underestimate the positive experiences of the children. We suggest that such a discrepancy in the assessment of dialogue experience might stem from a "non-participant bias" in facilitators.