there are some 2.4ghz choppers avalable on ebay I know someone who got one that was damaged and paid a £10 for it , this type
E-flite - Advancing Electric Flight - Blade CX2 RTF Electric Coaxial Micro Helicopter and took the radio gear out for a boat . may be an idea to contact one of the big suppliers of them and ask if they will sell or donate to the school.
peter