Alex, I suppose F3P planes could be dangerous if you were in a location where someone could be hit by the prop. I never fly in an area that is not 'controlled' or kids can get to without supervision. F3P planes are very light and slow but in the right circumstances could injure someone. My guess is the people you are trying to work with don't really understand the risks (or lack of) relative to other activities in gymnasiums. Properly managed/supervised, F3P should not be a dangerous activity.

Perhaps you could show those in charge a few videos of the F3P planes in flight, how slow they are, how light they are and work out a way to demonstrate what you are wanting to do.

Woodie