I am a student at Cumberland Perry Vocational School aI have recently obtained my commerical flight license. I assembled an S900 with an A3 flight controller; the point of the drone is to be used as an educational tool for the Criminal Justice students. Having begineers flying I would like to increase security from an accident. How can I limit the speed of my UAV?

I am a student at Cumberland Perry Vocational School aI have recently obtained my commerical flight license. I assembled an S900 with an A3 flight controller; the point of the drone is to be used as an educational tool for the Criminal Justice students. Having begineers flying I would like to increase security from an accident. How can I limit the speed of my UAV?