If people are so concerned about feeling left out surely the grand nature of a "Prom" for a bunch of relatively young children should be taken in to consideration? I naively thought they were the domain of 16-18 year old's leaving school!! Though that age was all about school plays, disco etc, was in my day! ( getting old!!!)
By the very nature that the event the school consents to there will be a distinct possibility of children turning up in 70k 4x4's performance cars Limo's etc so why not a helicopter?
As for not being of benifit to the rest of the children and making some feel left out..........
Why not ask the pilot to give a basic talk on how the machine works, what makes it fly? They cover Newtons laws very nicely !! That then could be applied to a lesson or two in the class room...I bet it would increase the concentration of alot of the pupils and the speed in which they learn with the excitement from seeing the machine
Could also have there pic's taken next to the heli and have a sit in the machine as well etc.... everyone could be involved and have a good and educational time, turning the event into a positive experience for everyone present.
